Power Systems glossary

This glossary provides terms and definitions for the IBM® Power Systems™ servers.

The following cross-references are used in this glossary:

  • See refers you from a term to a preferred synonym, or from an acronym or abbreviation to the defined full form.
  • See also refers you to a related or contrasting term.

For other terms and definitions, see the IBM Terminology website (opens in new window).

Special Characters

.tar file
A compressed file that uses a method of compression that compresses the entire file rather than breaking it up, often used for distributing open source code.


5250 display
Any display device that uses the 5250 data stream.
5250 emulation
Any one of many licensed programs that allow a personal computer to perform like a 5250 display station or printer and to use the functions of an IBM i operating system.


See alternating current.
See alternating current.
The ability to read, update, or otherwise use a resource. Access to protected resources is usually controlled by system software.
Pertaining to a resource that is currently operational.
A mechanism for connecting two unlike parts or machines, or for electrically or physically connecting a device to a computer or to another device.
advanced management module (AMM)
A hardware unit that provides system-management functions for all the blade servers in a BladeCenter chassis.
Advanced Peer-to-Peer Networking (APPN)
An extension to SNA that features distributed network control, dynamic definition of network resources, automated resource registration, and automated directory lookup. This network architecture supports the routing of data in a network between two or more Advanced Peer-to-Peer Communication (APPC) systems that do not need to be directly connected.
Advanced Program-to-Program Communication (APPC)
An implementation of the SNA LU 6.2 protocol that allows interconnected systems to communicate and share the processing of programs.
Advanced System Management Interface (ASMI)
A graphical interface that is part of the service processor firmware. The ASMI manages and communicates with the service processor. The ASMI is required to set up the service processor and to perform service tasks, such as reading service processor error logs, reading vital product data, and controlling the system power.
A UNIX operating system developed by IBM that is designed and optimized to run on POWER microprocessor-based hardware such as servers, workstations, and blades.
Pertaining to a character set that contains letters, digits, and usually other characters, such as punctuation marks.
alternate installation device
A tape device that is used to load Licensed Internal Code from the tape device to the load-source disk unit during a restore or installation operation. The alternate installation device can be on a different bus unit or on a different input/output processor (IOP) than the load-source disk unit.
alternate installation IPL
A special type of installation IPL (a D-mode IPL) in which the system uses the installation device to IPL itself. The system then copies the Licensed Internal Code from the alternate installation device to the load-source disk unit.
alternate IPL
The process of loading code into main storage from a designated input/output device instead of from the load-source disk unit for the system, and of preparing for system operations. An alternate IPL is a type D IPL.
alternating current (AC)
An electric current that reverses its direction at regularly recurring intervals.
alternative sector
A sector on the disk that is reserved by the system and then made available when a sector is damaged or defective.
American National Standards Institute (ANSI)
A private, nonprofit organization whose membership includes private companies, U.S. government agencies, and professional, technical, trade, labor, and consumer organizations. ANSI coordinates the development of voluntary consensus standards in the U.S.
American Standard Code for Information Interchange (ASCII)
A standard code used for information exchange among data processing systems, data communication systems, and associated equipment. ASCII uses a coded character set consisting of 7-bit coded characters.
See advanced management module.
Pertaining to data that consists of continuously variable physical quantities. See also digital.
See American National Standards Institute.
See authorized program analysis report.
See application programming interface.
See Advanced Program-to-Program Communication.
A hardware device with integrated software that is dedicated to a specific task or set of business requirements.
application programming interface (API)
An interface that allows an application program that is written in a high-level language to use specific data or functions of the operating system or another program.
See Advanced Peer-to-Peer Networking.
See American Standard Code for Information Interchange.
See Advanced System Management Interface.
See auxiliary storage pool.
An entire device or feature attached to a processing unit, including required adapters.
attended mode
An Operations Console state that requires the local console operator to approve each remote request for control of a System i product when the local console is in control.
attended mode IPL
A type of IPL in which the IPL stops at the dedicated service tools (DST) environment, allowing the user to make changes to the system or to debug a problem with the system. See also unattended mode IPL.
The right to access objects, resources, or functions.
To allow a user to communicate with or make use of an object, resource, or function.
authorized program analysis report (APAR)
A request for correction of a defect in a supported release of a program supplied by IBM.
auxiliary storage
All addressable storage other than main storage. See also memory.
auxiliary storage pool (ASP)
  1. One or more storage units that are defined from the storage devices or storage device subsystems that make up auxiliary storage. An ASP provides a way of organizing data to limit the effect of storage-device failures and to reduce recovery time.
  2. A group of disk units defined from the auxiliary storage devices. See also system ASP, user ASP.


A hardware part that has (in one or more planes) logic paths, low-voltage distribution paths, and grounding paths of a section of a machine.
  1. Pertaining to a system, device, file, or facility that can be used in the event of a malfunction or loss of data.
  2. A tape, diskette, or save file containing saved objects.
back up
To save information or objects on a system, usually to tape or diskette, for safekeeping.
backup console
A console that, in the event of a failure, can be used as the system console that manages the operating system. See also system console.
baseboard management controller (BMC)
A controller that monitors system platform management events such as fan failure and temperature or voltage increases, and logs their occurrence. The BMC is also used for hardware control, such as powering the node on and off.
basic input/output system (BIOS)
The code that controls basic hardware operations, such as interactions with diskette drives, hard disk drives, and the keyboard.
battery power unit
A source of electrical power that can be used when the normal utility power fails.
See basic input/output system.
See baseboard management controller.
To load an operating system or start the system.
British thermal unit (Btu)
The amount of heat required to raise a pound of water by 1 degree Fahrenheit.
British thermal unit per hour (Btu/hr.)
An English unit of measure for heat produced in one hour.
broadcast storm
A situation where one message that is broadcast across a network results in multiple responses. Each response generates more responses, causing excessive transmission of broadcast messages. Severe broadcast storms can block all other network traffic, but they can usually be prevented by carefully configuring a network to block illegal broadcast messages.
See British thermal unit.
See British thermal unit per hour.
bus-level partitioning
The dedicated allocation of an entire bus and all accompanying resources (input/output processors and input/output devices) to a particular logical partition. See also IOP-level partitioning.


See certificate authority.
call home
A communication link established between a product and a service provider. The product can use this link to place a call to a service provider when it requires service. With access to the machine, service personnel can perform service tasks, such as viewing error and problem logs or initiating trace and dump retrievals.
capacity on demand (CoD)
The ability of a computing system to increase or decrease its performance capacity as needed to meet fluctuations in demand.
capped partition
A logical partition in a shared processor pool whose processor use cannnot exceeds its assigned processing capacity.
An electronic circuit board that is plugged into a slot in a system to give it added capabilities.
See custom card identification number.
See compact disc.
See compact-disc read-only memory.
See central electronics complex.
Pertaining to a thermometric scale at which water boils at 100 degrees and freezes at 0 degrees in standard atmospheric pressure.
central electronics complex (CEC)
See central processor complex.
central processor complex (CPC)
A physical collection of hardware that consists of main storage, one or more central processors, timers, and channels.
certificate authority (CA)
A trusted third-party organization or company that issues the digital certificates. The certificate authority typically verifies the identity of the individuals who are granted the unique certificate.
A severe error inside a processor core that causes a processor core to stop all processing activities.
See customer installable feature.
See command-line interface.
A software program or computer that requests services from a server. See also host, server.
client logical partition
A logical partition that uses the I/O resources of another logical partition, for example, a logical partition that uses the resources of a Virtual I/O Server logical partition.
A set of independent systems or logical partitions (called nodes) that are organized into a network for the purpose of sharing resources and communicating with each other.
cluster-ready hardware server (CRHS)
A software component that provides management subsystem communication and methods for discovering components within a management subsystem.
cluster storage subsystem
A group of clusters where each cluster consists of one or more logical partitions that have a shared storage pool.
Cluster Systems Management (CSM)
Systems management software that is designed to scale to large-size clusters.
See capacity on demand.
command line
The blank line on a display where commands, option numbers, or selections can be entered.
command-line interface (CLI)
A computer interface in which the input and output are text based.
commercial processing workload (CPW)
An application that is run on System i models and processors to determine processor performance. The CPW workload is representative of commercial applications, particularly those that do significant database processing in conjunction with journaling and commitment control.
communication adapter
A device that allows network communication.
compact disc (CD)
An optical disc that stores digital data.
compact-disc read-only memory (CD-ROM)
High-capacity read-only memory in the form of an optically read compact disc.
Pertaining to the shared use of resources by multiple interactive users or application programs at the same time.
concurrent addition
The addition of hardware to a hardware unit while it is operational.
concurrent cold repair
Repair to hardware that is electrically isolated from the running system. The hardware that is isolated has no resources that are being used by the system when the repair is started.
concurrent hot repair
Repair to hardware that is electrically connected to the system. The hardware being repaired might have resources that are being used by the system when the repair is started.
concurrent maintenance
Service or maintenance that is performed on a hardware unit in the system while the system is fully or partially operational.
concurrent repair
Repair to hardware in a hardware unit while it is operational.
A plastic or metal piping system that is used to protect and route electrical wiring.
  1. The manner in which the hardware and software of a system, subsystem, or network are organized and interconnected.
  2. See topology.
  1. To describe the interconnected arrangement of the devices, programs, communications, and optional features installed on a system.
  2. To describe setting up auxiliary storage pools and checksum protection.
A device that coordinates and controls the operation of one or more input/output devices (such as workstations) and synchronizes the operation of such devices with the operation of the system as a whole.
control panel
A panel that contains lights and switches that are used to observe status and to operate or service the system.
  1. See central processor complex.
  2. See current processor capacity.
See commercial processing workload.
See cluster-ready hardware server.
See customer-replaceable unit.
See Cluster Systems Management.
current processor capacity (CPC)
The amount of processor capacity (in units of 1/100 of a physical processor) that is assigned to a logical partition.
  1. A movable symbol on a display, often a blinking or solid block of light, that identifies a choice to select, indicates where user interaction with the keyboard will appear, or indicates a position of interest on the display surface.
  2. A named control structure used by an application program to point to and select a row of data from a set.
custom card identification number (CCIN)
A unique alphanumeric number that is assigned many individual hardware parts or assemblies.
customer installable feature (CIF)
An assembly or part that a customer can replace.
customer-replaceable unit (CRU)
An assembly or part that can be replaced in its entirety by a user when any one of its components fails.


data center
A centralized repository of data and information relating to a particular field of knowledge.
data migration
The movement of data when the software is upgraded or the data is transferred to a different hardware server or model.
See decibel.
A family of IBM licensed programs for relational database management.
See device driver.
decibel (dB)
A unit of signal strength or loudness, such as the signal on a data communications channel.
dedicated service tools (DST)
Service functions that are available only from the console and that can run when the operating system is not available, as well as when the operating system is available.
The process of running a software utility to rewrite fragmented data to contiguous sectors of a computer storage medium to improve access and retrieval time.
A piece of equipment such as a workstation, printer, disk drive, tape unit, or remote system.
device configuration
The physical placement of display stations, printers, and so forth; and the configuration descriptions that describe the physical configuration to the system and describe how the configuration will be used by the system.
device driver (DD)
A program that provides an interface between a specific real or virtual device and the application program that uses the device.
See Dynamic Host Configuration Protocol.
Pertaining to data in the form of digits. See also analog.
digital versatile disc (DVD)
An optical disc that has the same overall dimensions of a CD-ROM, but has significantly higher capacities than a CD-ROM. DVDs are also double sided, whereas CD-ROMs are single sided.
digital video disc
See digital versatile disc.
See dual inline memory module.
disk drive
The mechanism used to read and write information on a disk.
A thin, flexible magnetic plate that is permanently sealed in a protective cover. It can be used to store information copies from the disk or another diskette.
disk unit enclosure
A physical enclosure containing one or more disk units.
display station
A device, usually equipped with a keyboard and a display device, capable of sending and receiving information over a communications line. See also workstation.
The optical connections between supernodes for forming an HPC cluster.
See dynamic LPAR.
domain name
In Internet communications, a name of a host system. A domain name consists of a sequence of subnames that are separated by a delimiter character, for example, www.ibm.com.
See dedicated service tools.
dual inline memory module (DIMM)
A small circuit board with memory-integrated circuits containing signal and power pins on both sides of the board. See also single inline memory module.
See digital versatile disc.
Dynamic Host Configuration Protocol (DHCP)
A communications protocol that is used to centrally manage configuration information. For example, DHCP automatically assigns IP addresses to computers in a network.
dynamic IP address
A temporary IP address for a transient device or logical unit on a network: for example, a personal computer. See also IP address.
dynamic LPAR (DLPAR)
The ability to move processors, memory, and interactive performance between logical partitions without restarting a logical partition or the server. See also logical partition, managed system.


See electronic customer support.
See Electronic Industries Alliance.
EIA unit
A unit of measure, established by the Electronic Industries Association, equal to 44.45 millimeters (1.75 inches).
electronic customer support (ECS)
A part of the operating system that allows a customer to access the question-and-answer (Q & A) function; problem analysis, reporting, and management; IBM product information; and technical information exchange.
Electronic Industries Alliance (EIA)
An organization of electronics manufacturers that advances the technological growth of the industry, represents the views of its members, and develops industry standards.
Electronic Service Agent (ESA)
A function that provides automatic hardware problem-reporting to help predict and prevent hardware errors by early detection of potential problems. With this function, users can also download fixes and automatically submit problems to IBM when appropriate.
electrostatic discharge (ESD)
The flow of current that results when objects having a static charge come into close enough proximity to discharge.
The use of software, hardware, or both by one system to imitate another system. The imitating system accepts the same data, runs the same programs, and achieves the same results as the imitated system.
enclosure services manager (ESM)
The main control unit within a cache expansion drawer. It is a redundant and hot-swappable SAS communication FRU that provides SAS expander and SES functions.
Enhanced 5250 Emulation
A program that allows a personal computer and a printer to be attached to a System i product and perform the functions of one or two 5250 workstations on one twinaxial cable. The workstations can be one display station, two display stations, or one display station and one printer.
entitled memory
The maximum amount of physical memory that is guaranteed to be available for I/O mapping by a logical partition at any given time.
ephemeral port
A temporary port assigned by a server's IP stack from a designated range of ports.
See Electronic Service Agent.
See electrostatic discharge.
See enclosure services manager.
A packet-based networking technology for local area networks (LANs) that supports multiple access and handles contention by using Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as the access method. Ethernet is standardized in the IEEE 802.3 specification. See also local area network.
expansion unit
A machine type or feature that can be connected to a system unit to provide additional storage and processing capacity. This expansion unit may contain I/O hardware such as cards, tapes, and disk drives.


A complex network of hubs, switches, adapter endpoints, and connecting cables that support a communication protocol between devices. For example, Fibre Channel uses a fabric to connect devices.
fabric manager
Software that initializes and monitors communications network components.
facsimile machine (fax machine)
A functional unit that converts images to signals for transmission over a telephone system or that converts received signals back to images.
An automatic operation that switches to a redundant or standby system or node in the event of a software, hardware, or network interruption.
Fast Ethernet
An Ethernet standard that provides a data rate of 100 Mbps.
  1. To transmit an image, using a telephone system and facsimile machines.
  2. The printed copy received from a facsimile machine.
fax machine
See facsimile machine.
  1. See Fibre Channel.
  2. See feature code.
Part of a product that is either included with the product or can be ordered separately.
feature code (FC)
A code used by IBM to process hardware and software orders.
fiber optic
Describing a transmission medium composed of a glass fiber light path surrounded by a cladding material that confines the signal to the light path.
fiber optic cable
A fiber or bundle of fibers in a structure built to meet optic, mechanical, and environmental specifications.
Fibre Channel (FC)
A technology for transmitting data between computer devices. It is especially suited for attaching computer servers to shared storage devices and for interconnecting storage controllers and drives.
field-replaceable unit (FRU)
An assembly or part that is replaced in its entirety by service personnel when any one of its components fails.
A collection of related data that is stored and retrieved by an assigned name.
A network configuration, typically both hardware and software, that prevents unauthorized traffic into and out of a secure network.
flash memory
A computer storage medium that retains its data when the power is turned off and that can be electronically erased and reprogrammed without being removed from the circuit board.
flexible service processor (FSP)
Firmware that provides diagnostics, initialization, configuration, runtime error detection, and correction. The flexible service processor connects the managed system to the Hardware Management Console.
The amount of computer storage that is occupied by a computer program. For example, if a program occupies a large amount of storage, it has a large footprint.
frame buffer
A quantity of video RAM (VRAM) that is used to store the image displayed on the monitor. The frame buffer is the electronic canvas on which every drawing primitive is drawn.
free space
The total amount of unused space in a page, data set, file, storage medium, or file system. Free space is the space that is not used to store records, control information, or files.
See field-replaceable unit.
See flexible service processor.
full paging
The final phase of the IPL sequence, in which all functions can access all data on all disk units in the ASP. See also limited paging, prestatic paging, static paging.


general-purpose processor core
A licensed processor core other than a Power IFL processor core. The AIX, IBM i, VIOS, and Linux partitions can be run on a general-purpose processor core.
A program to download microcode to a specific adapter or device. This program is provided with a microcode update.
graphical user interface (GUI)
A computer interface that presents a visual metaphor of a real-world scene, often of a desktop, by combining high-resolution graphics, pointing devices, menu bars and other menus, overlapping windows, icons and the object-action relationship.
graphics processor unit
A specialized processor designed to rapidly manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display.
See graphical user interface.
GX adapter
An I/O hub that connects I/O adapters to the processor and to memory in the system.


See high availability.
hard disk
A nonremovable storage medium used for storage of data on a personal computer.
hard disk drive (HDD)
A stand-alone disk drive that reads and writes data on rigid disks and can be attached to a port on the system unit.
Hardware Management Console (HMC)
A system that controls managed systems, including the management of logical partitions and use of Capacity Upgrade on Demand. Using service applications, the HMC communicates with managed systems to detect and consolidate information, which can then be sent for analysis. See also managed system.
hardware service manager (HSM)
A tool for displaying and working with system hardware from both a logical and a packaging viewpoint, for debugging input/output processors (IOPs) and devices, and for fixing failing and missing hardware.
See host bus adapter.
See host channel adapter.
See hard disk drive.
In AIX, a logical unit number (LUN) on an array.
See Host Ethernet Adapter.
See hexadecimal.
hex, HEX
See hexadecimal.
hexadecimal (hex, hex, HEX)
Pertaining to a numbering system that has a base of 16.
high availability (HA)
  1. Pertaining to a clustered system that is reconfigured when node or daemon failures occur so that workloads can be redistributed to the remaining nodes in the cluster.
  2. The ability of IT services to withstand all outages and continue providing processing capability according to some predefined service level. Covered outages include both planned events, such as maintenance and backups, and unplanned events, such as software failures, hardware failures, power failures, and disasters.
high-performance computing (HPC)
A technology that requires massive computational powers, such as supercomputers or computer clusters, to solve complex problems.
high-speed link (HSL)
A hardware connectivity architecture that links system processors to system I/O buses and other systems. See also remote input/output.
high-speed link loop
The system-to-expansion-unit connectivity technology that is required to implement switchable independent disk pools residing on an expansion unit. The servers and expansion units in a cluster that uses resilient devices on an external expansion unit must be on an HSL loop that is connected with HSL cables.
See Hardware Management Console.
HMC 5250 console
An emulation session to a logical partition's operating system.
  1. A computer that is connected to a network and that provides an access point to that network. The host can be a client, a server, or both a client and server simultaneously. See also client, server.
  2. The controlling or highest-level system in a data communications configuration.
host bus adapter (HBA)
An interface card that connects a host bus, such as a peripheral component interconnect (PCI) bus, to the storage area network.
host channel adapter (HCA)
Based on InfiniBand technology, a port connection on a system allowing a network fabric interconnect.
Host Ethernet Adapter (HEA)
A physical Ethernet adapter that is integrated directly into the GX+ bus on a managed system. HEAs offer high throughput, low latency, and virtualization support for Ethernet connections.
host name
In Internet communication, the name given to a computer. The host name might be a fully qualified domain name such as mycomputer.city.company.com, or it might be a specific subname such as mycomputer. See also IP address.
host stack
The collection of software that runs from the driver through the middleware and that provides the communications fabric protocols to be used by applications.
Pertaining to redundant hardware (such as an adapter, a disk, a drive, or a server) that is installed and available in the event of a hardware failure.
Pertaining to a device that is capable of being replaced while the system is on.
hot swap
To replace a hardware component without turning off the system.
See high-performance computing.
See high-speed link.
See hardware service manager.
A point, or piece of hardware, that connects multiple devices in a network.
Software or a physical device that enables multiple instances of operating systems to run simultaneously on the same hardware.


The IBM licensed program that was used as the operating system for System i servers. The predecessor to i5/OS was Operating System/400 (OS/400). See also IBM i, Operating System/400, System i.
See integrated battery feature.
The IBM licensed program that is the integrated operating system for Power Systems servers. It integrates such functions as relational database, security, web services, networking, and storage management capabilities. The predecessor to IBM i was i5/OS, which was preceded by Operating System/400 (OS/400). See also i5/OS, Operating System/400, System i.
See Internet Control Message Protocol.
A graphical representation of an object (for example, a file or program) that consists of an image, an image background, and a label.
initial program load (IPL)
The process that loads the system programs from the system auxiliary storage, checks the system hardware, and prepares the system for user operations.
input/output adapter (I/O adapter, IOA)
A functional unit or a part of an I/O controller that connects devices to an I/O processor.
input/output data
Data provided to the computer or data resulting from computer processing.
input/output processor (I/O processor, IOP)
A processor dedicated to controlling channels or communication links.
integrated battery feature (IBF)
Battery backup hardware that protects against power line disturbances such as short-term power loss or brown-out conditions.
Integrated Virtual Ethernet adapter (IVE adapter)
See Host Ethernet Adapter.
Integrated Virtualization Manager (IVM)
A browser-based management interface that is used to manage a System p or blade server. The IVM can be used to create logical partitions, manage virtual resources such as storage, and view service information related to the server.
Integrated xSeries Adapter (IXA)
A PCI expansion card that can be installed in selected System x models and that provides a high-speed link to a System i product.
Intelligent Platform Management Interface (IPMI)
A standard for controlling intelligent devices that monitor a system. It provides for dynamic discovery of sensors in the system and the ability to monitor the sensors and be informed when the sensor's values change or go outside certain boundaries.
The worldwide collection of interconnected networks that use the Internet suite of protocols and permit public access.
Internet Control Message Protocol (ICMP)
An Internet protocol that is used by a gateway to communicate with a source host, for example, to report an error in a datagram.
Internet Protocol (IP)
A protocol that routes data through a network or interconnected networks. This protocol acts as an intermediary between the higher protocol layers and the physical network. See also Transmission Control Protocol.
  1. An identification that is used to send a signal to the processor indicating that the installed hardware requires attention.
  2. A signal sent by an I/O device to the processor when an error has occurred or when assistance is needed to complete I/O. An interrupt usually suspends the running of the program that is currently running.
An organization's internal network that uses the IP protocol.
Pertaining to interfaces or links within a rack of servers or switches.
See input/output adapter.
I/O adapter
See input/output adapter.
I/O hub
A device that provides the interface between the processors and memory in the central electronics complex and the I/O drawers that are connected to it.
See input/output processor.
IOP-level partitioning
A dedicated allocation of the input/output processor (IOP) and all accompanying resources (input/output devices) to a particular logical partition. IOPs on a single bus may be dedicated to different logical partitions. The bus resources that contain these IOPs must be shared. See also bus-level partitioning.
I/O processor
See input/output processor.
I/O server
Software that provides I/O service to other logical partitions on the same system.
See Internet Protocol.
IP address
A unique address for a device or logical unit on a network that uses the Internet Protocol standard. See also dynamic IP address, host name, static IP address.
See initial program load.
See Intelligent Platform Management Interface.
isolation procedure
Written information used by service representatives to repair IBM equipment. An isolation procedure contains yes/no questions and procedures that direct the user to the failing part of the equipment.
IVE adapter
See Integrated Virtual Ethernet adapter.
See Integrated Virtualization Manager.
See Integrated xSeries Adapter.


A small piece of plastic-covered metal that is used to connect two contacts and complete a circuit.


In OSI, a session-layer functional unit that supports the basic session services required to establish connections, transfer normal data, and release connections.
kernel-based virtual machine (KVM)
An open source virtualization software for Linux that is based on hardware virtualization extensions (Intel VT-X and AMD-V) and a modified version of QEMU.
A cryptographic mathematical value that is used to digitally sign, verify, encrypt, or decrypt a message. See also private key, public key.
key ring
In computer security, a file that contains public keys, private keys, trusted roots, and certificates.
key ring file
A binary file that is protected by a password and stores one or more certificates on the server hard drives. There are two types of key ring files: server and CA.
In security, a file or a hardware cryptographic card where identities and private keys are stored, for authentication and encryption purposes. Some keystores also contain trusted or public keys.
keystore file
A key ring that contains both public keys that are stored as signer certificates and private keys that are stored in personal certificates.
keytab file
A file on the service's host system that contains entries each of which contains the service principal's name and encrypted secret key.
kilovolt-ampere (kVA)
A unit of power.
See kilovolt-ampere.
See kernel-based virtual machine.


See local area network.
See Lightweight Directory Access Protocol.
A switch field replaceable unit (FRU) that plugs into a switch chassis. It contains connectors for interconnecting with adapters and other switches. Internal to the switch chassis, a leaf connects to spine modules, which provide connectivity to other leaf FRUs in the same switch chassis by way of a midplane.
leaf card
A card internal to a switch chassis that provides external connectivity by using cable connectors, and that provides internal communication to spines as a path to other leaf cards.
leaf module
A leaf card in a switch chassis that contains a specific number of InfiniBand port connectors and has the capability of communicating with other leaf modules through connections to spines.
leaf switch chip
A chip that provides communication paths and switching between the paths and that populates a leaf card.
See light-emitting diode.
See Licensed Internal Code.
A legal agreement that authorizes the use of proprietary information including, but not limited to, copyrighted or patented information.
Licensed Internal Code (LIC)
The layered architecture below the machine interface (MI). The Licensed Internal Code is a proprietary system design that carries out many functions. These functions include but are not limited to storage management, pointers and addressing, program management functions, exception and event management, data functions, I/O managers, and security.
Licensed Internal Code fix
A temporary solution to, or bypass of, a defect in a current release of the Licensed Internal Code.
licensed program (LP)
A separately priced program and its associated materials that have a copyright and are offered to customers under the terms and conditions of a licensing agreement.
light-emitting diode (LED)
A semiconductor chip that gives off visible or infrared light when activated.
Lightweight Directory Access Protocol (LDAP)
An open protocol that uses TCP/IP to provide access to directories that support an X.500 model and that does not incur the resource requirements of the more complex X.500 Directory Access Protocol (DAP). For example, LDAP can be used to locate people, organizations, and other resources in an Internet or intranet directory.
limited paging
A phase of the IPL sequence that takes place prior to full paging during which only the data on the load-source disk unit can be accessed by the normal Licensed Internal Code functions. See also full paging, prestatic paging, static paging.
line description
An object that contains information describing a particular communications line that is attached to the system. The system-recognized identifier for the object type is *LIND.
link aggregation
The grouping of physical network interface cards, such as cables or ports, into a single logical network interface. Link aggregation is used to increase bandwidth and network availability.
Live Partition Mobility (LPM)
A component of the PowerVM Enterprise Edition hardware feature that provides the ability to move AIX, IBM i, and Linux logical partitions from one system to another. The mobility process transfers the system environment, which includes the processor state, memory, attached virtual devices, and connected users.
The connections between the hub switch chips that are located within a supernode.
load-source disk unit
The disk unit that contains the Licensed Internal Code for the system. This unit is always identified as unit number 1 in the disk configuration displays.
local area network (LAN)
A network that connects several devices in a limited area (such as a single building or campus) and that can be connected to a larger network. See also Ethernet.
logical memory
The address space, assigned to a logical partition, that the operating system perceives as its main storage. For a shared memory partition, a subset of the logical memory is backed up by physical main storage, and the contents of the remaining logical memory are kept in secondary storage.
logical partition (LP, LPAR)
One or more virtualized images of a hardware computing system that can include shared and dedicated resources assigned from the pool of resources available on a physical server. Each image appears to the operating system running within it to be a unique instance of a physical server. See also dynamic LPAR, virtual server.
logical partition firmware
The code that is loaded into an AIX or Linux logical partition from the server firmware.
logical partitioning
A function of an operating system that creates segments of resources that can be run on copies, or instances, of the operating system and associated applications.
logical unit number (LUN)
In the Small Computer System Interface (SCSI) standard, a unique identifier used to differentiate devices, each of which is a logical unit (LU).
  1. See licensed program.
  2. See logical partition.
See logical partition.
See Live Partition Mobility.
See logical unit number.


See Media Access Control.
main storage
See memory.
main storage dump (MSD)
A process of collecting data from the system's main storage. It can be done automatically by the service processor as a result of a system failure, or it can be performed manually by the operator when there appears to be a system failure.
maintenance analysis procedure (MAP)
In hardware maintenance, a step-by-step procedure that assists an IBM service representative to trace a symptom to the cause of the failure.
managed system
A system that is being controlled by a given system management application. See also dynamic LPAR, Hardware Management Console.
management server (MS)
A server on which the systems management software runs.
manual IPL
See attended mode IPL.
See maintenance analysis procedure.
See megabyte.
See multiple chip module.
Magnetic disks, magnetic tapes, compact discs (CDs), and digital video disks (DVDs).
Media Access Control (MAC)
In networking, the lower of two sublayers of the Open Systems Interconnection model data link layer. The MAC sublayer handles access to shared media, such as whether token passing or contention will be used.
megabyte (MB)
For processor storage, real and virtual storage, and channel volume, 2 to the 20th power or 1,048,576 bytes. For disk storage capacity and communications volume, 1,000,000 bytes.
Program-addressable storage from which instructions and other data can be loaded directly into registers for subsequent running or processing. See also auxiliary storage.
memory affinity
A feature available in AIX to allocate memory attached to the same multiple chip module (MCM) on which the process runs. Memory affinity improves the performance of applications on some IBM Power Systems servers.
memory weight
A relative value that is one of the factors in determining the allocation of physical memory to the shared memory partitions. A higher value relative to the values set for other shared memory partitions increases the probability of the hypervisor allocating more physical memory to the shared memory partition.
A displayed list of items from which a user can make a selection.
See miscellaneous equipment specification.
See multifunction IOP.
A logical partition that uses a partial processor. With Micro-Partitioning technology, a partition can be as small as 1/20th of a processor or can consist of full plus partial processors.
Software that acts as an intermediate layer between applications or between client and server. It is used most often to support complex, distributed applications in heterogeneous environments.
  1. To move data from one location to another.
  2. To install a new version or release of a program to replace an earlier version or release.
miscellaneous equipment specification (MES)
A hardware change that is made after the time of the initial order.
mobile partition
A logical partition that can be moved from the source server to the destination server.
modular water unit (MWU)
A unit that circulates water, chilled by the heat exchanger, and distributes it to the nodes.
See management server.
See main storage dump.
multifunction IOP (MFIOP)
A system processor that as a unit contains more than one processor function such as a diskette controller, a storage device controller, and a communications controller.
multiple chip module (MCM)
The fundamental processor building block of some IBM Power Systems servers.
See modular water unit.


N_Port ID Virtualization (NPIV)
A standard method for virtualizing a physical Fibre Channel port.
See network address translation.
navigation bar
A set of links to other web pages in a website. For example, a navigation bar is typically located across the top or down the side of a page and contains direct links to the major sections within the website.
navigation tree
A hierarchical structure that is used to access information.
Any valid configuration of processors for a system that is capable of supporting 1 - n processors.
A system of resources, such as appliances, computers, and storage devices, that are connected virtually or physically.
network address translation (NAT)
  1. The conversion of a network address that is assigned to a logical unit in one network into an address in an adjacent network. See also static network address translation.
  2. In a firewall, the conversion of secure Internet Protocol (IP) addresses to external registered addresses. This enables communications with external networks but masks the IP addresses that are used inside the firewall.
network administrator
A person who defines the network configuration and other network-related information. This person controls how an enterprise or system uses its network resources.
network boot
The process of starting a computer directly over the network rather than from a disk.
Network Installation Management (NIM)
An environment that provides installation and configuration of software within a network interface.
network interface controller (NIC)
Hardware that provides the interface control between system main storage and external high-speed link (HSL) ports.
network server description (NWSD)
An object that contains a description of the characteristics of a file server I/O processor that is attached to the system.
Network Time Protocol (NTP)
A protocol that synchronizes the clocks of computers in a network.
See network interface controller.
See Network Installation Management.
  1. In networking, a point capable of sending and receiving data. A node can be a device, such as printer or workstation, a system, or a storage location on a disk.
  2. A grouping of processor, memory, and I/O hub hardware resources in the system. On systems of machine type FHA, a node is a processor book. On systems of machine type MMA, a node is a drawer.
  3. In communications, an end point of a communication link or a junction common to two or more links in a network. Nodes can be processors, communication controllers, cluster controllers, terminals, or workstations. Nodes can vary in routing and other functional capabilities.
nonconcurrent repair
Repair to hardware in a hardware unit when the power is off.
nonprogrammable workstation (NWS)
A workstation that does not have processing capability and does not allow the user to change its functions.
See N_Port ID Virtualization.
See Network Time Protocol.
See nonprogrammable workstation.
See network server description.


See original equipment manufacturer.
A unit of measure of electrical resistance.
See online transaction processing.
online transaction processing (OLTP)
A type of interactive application in which requests that are submitted by users are processed as soon as they are received. Results are returned to the requester in a relatively short period of time.
See Open Power Abstraction Layer.
Open Power Abstraction Layer (OPAL)
Low-level firmware for scale-out IBM Power Systems.
operating system (OS)
A collection of system programs that control the overall operation of a computer system.
Operating System/400 (OS/400)
The IBM licensed program that was used as the operating system for iSeries servers. See also i5/OS, IBM i.
Operations Console
A feature of System i Access for Windows that provides the ability for a System i console to be either a local or a remote personal computer. With Operations Console, a system administrator, for example, can access the console from home.
operator panel
See control panel.
optical device
Either a CD-ROM drive, a digital video disc (DVD), or both.
  1. A feature of the IBM i operating system that allows a user to connect multiple System i systems by using SPD bus, high-speed link (HSL) loop, or virtual interpartition technologies.
  2. A System i system area network (SAN) that allows high-speed links between systems in a System i cluster. OptiConnect provides three hardware technologies (SPD OptiConnect, high-speed link (HSL) OptiConnect, and virtual OptiConnect) that can exist simultaneously on a single cluster node.
original equipment manufacturer (OEM)
A manufacturer of equipment that can be marketed by another manufacturer.
See operating system.
See Operating System/400.


paging service partition
A Virtual I/O Server (VIOS) logical partition that provides access to the paging space devices for the shared memory partitions.
paging space
Area of nonvolatile storage used to hold portions of the shared memory partition's logical memory that are not resident in the shared memory pool.
paging space device
A physical or logical device that is used by the Virtual I/O Server to provide the paging space for a shared memory partition.
See product activity log.
parity update footprint
A nonvolatile entry that indicates whether the RAID parity is out of synchronization with its associated data, for example, while performing a write operation to the RAID array.
A logical division of storage on a fixed disk.
In computer and network security, a specific string of characters used by a program, computer operator, or user to access the system and the information stored within it.
See Peripheral Component Interconnect.
PCI bridge
A device that connects one or more subordinate PCI buses to a primary PCI bus. The PCI bus that is closest to the system processor is the primary PCI bus, and the subordinate buses are secondary PCI buses.
PCI bridge set
A set of PCI card positions.
See Peripheral Component Interconnect Express.
PCI Express
See Peripheral Component Interconnect Express.
PCI host bridge (PHB)
A device that merges data from PCI bridges for delivery to the system processor.
See Peripheral Component Interconnect-X.
See physical device.
See Portable Document Format.
Peripheral Component Interconnect (PCI)
A local bus that provides a high-speed data path between the processor and attached devices. See also Peripheral Component Interconnect Express, Peripheral Component Interconnect-X.
Peripheral Component Interconnect Express (PCI Express, PCIe)
A local serial interface that provides a high-speed data path between the processor and attached devices. Unlike previous PCI implementations that used a parallel bus architecture, PCI Express uses point-to-point serial links called lanes. See also Peripheral Component Interconnect.
Peripheral Component Interconnect-X (PCI-X)
An enhancement to the Peripheral Component Interconnect (PCI) architecture. PCI-X enhances the Peripheral Component Interconnect (PCI) standard by doubling the throughput capability and providing additional adapter-performance options while maintaining backward compatibility with PCI adapters. See also Peripheral Component Interconnect.
See PCI host bridge.
physical device (PDev)
An I/O device that is assigned to a logical partition and that is used directly.
pinned memory
A page in memory that is always available for the applications that are in physical memory.
A hardware part that has (in one or more planes) logic paths, low-voltage distribution paths, or grounding paths of a section of a machine.
The combination of an operating system and hardware that makes up the operating environment in which a program runs.
Point-to-Point Protocol (PPP)
A data-link protocol for communication between two computers that use a serial interface, typically a personal computer connected by telephone line to a server.
A hardware interface to which an I/O device is attached for the purpose of sending and receiving data.
Portable Document Format (PDF)
A standard specified by Adobe Systems, Incorporated, for the electronic distribution of documents. PDF files are compact; can be distributed globally via email, the web, intranets, or CD-ROM; and can be viewed with the Acrobat Reader.
See power-on self-test.
power cord
The electrical connection between the AC power source and the computer.
power down
A CL command to turn the power off and bring an orderly end to system operation.
Power IFL
See Power Integrated Facility for Linux.
Power IFL processor core
A licensed processor core that is enabled by feature code ELJ1 on IBM Power Systems servers. Each Power IFL processor core feature enables one processor core. Only the Linux operating system can be run on Power IFL processor cores.
Power Integrated Facility for Linux (Power IFL)
An optional lower cost per processor core activation for Linux-only workloads on IBM Power Systems servers.
power-on light
The light on the operator panel that indicates that the DC power in the system is functioning.
power-on self-test (POST)
A series of internal diagnostic tests activated each time the system power is turned on.
PowerVM Active Memory Sharing
A technology that enables logical partitions to share the memory in the shared memory pool.
See Point-to-Point Protocol.
preloaded system
A system that is shipped with the licensed programs and program temporary fixes (PTFs) already installed on the disk.
prestatic paging
A phase of the IPL sequence that takes place prior to static paging, where normal Licensed Internal Code functions cannot access data from any disk (neither load-source nor non-load-source disk units). See also full paging, limited paging, static paging.
private key
An algorithmic pattern used to encrypt messages that only the corresponding public key can decrypt. The private key is also used to decrypt messages that were encrypted by the corresponding public key. The private key is kept on the user system and is protected by a password. See also key, public key.
private network
A network established and operated by a private organization or corporation for users within that organization or corporation. See also public network.
problem analysis
The process of finding the cause of a problem. For example, a program error, device error, or user error.
A device for processing data from programmed instructions. It may be part of another unit.
processor core
A single processing unit on a chip with multiple processing units.
product activity log (PAL)
A log of system data, Licensed Internal Code data, software components, subsystem information, and I/O device data.
programmable workstation
A workstation that has some degree of processing capability and allows the user to change its functions.
program temporary fix (PTF)
For System i, System p, and System z products, a package containing individual or multiple fixes that is made available to all licensed customers. A PTF resolves defects and might provide enhancements.
A message or a displayed symbol that requests information or user action. The user must respond to allow the program to proceed.
See program temporary fix.
public key
An algorithmic pattern used to decrypt messages that were encrypted by the corresponding private key. A public key is also used to encrypt messages that can be decrypted only by the corresponding private key. Users broadcast their public keys to everyone with whom they must exchange encrypted messages. See also key, private key.
public network
Generically, a network operated by common carriers or telecommunications administrators for the provision of circuit-switched, packet-switched, and nonswitched lines to the public. See also private network.


An open source emulator for complete PC systems. In addition to emulating a processor, QEMU permits emulation of all necessary subsystems, such as networking and video hardware, as well as advanced concepts.
To end a process or shut down a system after allowing normal completion of active operations.


A free-standing structure or frame that can hold multiple servers and expansion units.
rack stabilizer
A plate that holds the rack stable or steady when a device is pulled out for service.
See Redundant Array of Independent Disks.
A form of parity RAID in which the disks operate independently, the data stripe size is no smaller than the exported block size, and parity check data is distributed across the array's disks.
A form of RAID that can continue to process read and write requests to all of an array's virtual disks in the presence of two concurrent disk failures.
Hardware attached inside a rack to hold devices that are designated as installable in a rack.
raw device
In UNIX-based operating systems, a block device that handles data as a stream of bytes, rather than as a block.
See role-based access control.
A hollowed electrical fitting that contains the live parts of a circuit.
Redundant Array of Independent Disks (RAID)
A collection of two or more physical disk drives that present to the host an image of one or more logical disk drives. In the event of a physical device failure, the data can be read or regenerated from the other disk drives in the array due to data redundancy.
reference code
A group of characters that identifies the machine status or a specific error condition.
A distribution of a new product or new function and authorized program analysis report (APAR) fixes for an existing product. The first version of a product is announced as release 1 modification level 0.
Pertaining to a system, program, or device that is accessed through a communication line.
remote control panel
A graphical interface that is provided by Operations Console that allows control panel operations to be performed from a remote location. This interface allows personal computer access to the control panel that controls operating or servicing the system.
remote input/output (RIO)
A type of hardware architecture that facilitates faster input/output connection speeds between a system and expansion units. See also high-speed link.
remote restart
The function that restarts a logical partition on a different physical server during a server outage.
removable media
Volumes that can be removed from the hardware devices (such as tape cartridges and optical disks) where they are read and written.
Resource Monitoring and Control (RMC)
A subsystem that runs on each cluster node and provides global access to subsystems and resources throughout the cluster, thus providing a single monitoring and management infrastructure.
See remote input/output.
See Resource Monitoring and Control.
role-based access control (RBAC)
The process of restricting integral components of a system based on user authentication, roles, and permissions.


See serial-attached SCSI.
SAS expander
A component that facilitates switchable communication paths between multiple SAS devices.
See Small Computer System Interface.
SCSI Enclosure Services (SES)
A subset of the small computer system interface (SCSI) protocol used to monitor temperature, power, and fan status for enclosure devices.
See Synchronous Data Link Control.
See shared Ethernet adapter.
Secure Shell (SSH)
A network protocol for secure data exchange between two networked devices. The client can use public-key and private-key authentication, or password authentication, to access the remote server.
serial-attached SCSI (SAS)
A data-transfer technology that moves data to and from computer storage devices. Serial-attached SCSI uses a point-to-point serial protocol, which replaces the traditional, parallel SCSI bus technology.
A software program or a computer that provides services to other software programs or other computers. See also client, host.
server firmware
The code that resides in system flash memory, and includes a number of subcomponents, including POWER Hypervisor, power control, service processor, and logical partition firmware that is loaded into either AIX or Linux logical partitions.
server-side include (SSI)
A facility for including dynamic information in documents sent to clients, such as current date, the last modification date of a file, and the size or last modification of other files.
service action log
A utility that displays entries requiring action by a service representative.
service authority
A special authority that allows the user to perform the alter function in the service functions.
Service Focal Point
An application on the Hardware Management Console (HMC) that collects problems from the system and from logical partitions. It is used to view problems and to take action on problems.
service processor
  1. The logic that contains the processor function to start the system processor and handle error conditions.
  2. The interface to the Hardware Management Console (HMC) that provides hardware control and logical partition (LPAR) support for IBM Power Systems servers.
service provider (SP)
Any company that provides services for a fee to its customers, such as telecommunication companies, application service providers, enterprise IT, and Internet service providers.
service request number (SRN)
A code that is used by service technicians or the customer to determine the failing area of the system.
service tools device ID
A programming object used by both the PC and the IBM System i model as a means to authenticate the network connection between the two. A service tools device ID is unique to that PC and server connection. The service tools device ID can be managed by authorized users in dedicated service tools (DST) or system service tools (SST). The default service tools device ID is QCONSOLE.
See SCSI Enclosure Services.
shared Ethernet adapter (SEA)
A Virtual I/O Server (VIOS) component that connects a physical Ethernet adapter and one or more virtual Ethernet adapters.
shared memory
Physical memory that is assigned to a shared memory pool and shared among multiple logical partitions.
shared memory pool
A defined collection of physical memory blocks that are managed as a single memory pool by the hypervisor.
shared processor pool
A group of physical processors that provide processing capacity that can be shared among multiple logical partitions. Processing capacity from the shared processor pool can be assigned to each of the logical partitions in partial processor increments. The sum of the assigned processing capacity across all logical partitions in the shared processor pool cannot exceed the total processing capacity of the shared processor pool.
shared storage pool
A storage pool that provides distributed storage access to one or more logical partitions or virtual servers in a cluster or that can be shared by more than one subsystem.
short host name
The system or machine name portion of a fully qualified host name; for example, in the fully qualified host name "system1.mysite.mycompany.com," the short host name is "system1."
See single inline memory module.
single inline memory module (SIMM)
In computer hardware, a small circuit card that carries a number of surface-mounted memory chips in a space-saving configuration with the connector pins protruding in a single line from the edge of the card. Varying numbers of SIMMs can be plugged easily into slots in a memory board to expand random access memory. See also dual inline memory module.
single root I/O virtualization (SR-IOV)
A Peripheral Component Interconnect (PCI) Special Interest Group specification to allow multiple partitions that are running simultaneously within a single computer to share a Peripheral PCI Express (PCIe) device.
The time difference between two clocks or clock values.
Small Computer System Interface (SCSI)
An ANSI-standard electronic interface that allows personal computers to communicate with peripheral hardware, such as disk drives, tape drives, CD-ROM drives, printers, and scanners faster and more flexibly than previous interfaces.
See symmetric multiprocessor.
See system management services.
See Systems Network Architecture.
An image that is an exact copy of the original files or directories from which it was created.
solid-state drive (SSD)
A data storage device that uses solid-state memory to store persistent data.
source server
A server that is being upgraded with new hardware or software or whose data is being migrated.
See service provider.
See system power control network.
A card internal to a switch chassis that provides connectivity between leaf cards.
See system reference code.
See single root I/O virtualization.
See service request number.
See solid-state drive.
See Secure Shell.
See server-side include.
See system service tools.
static IP address
A fixed IP address for a persistent device or logical unit on a network that uses the IP standard. See also IP address.
static NAT
See static network address translation.
static network address translation (static NAT)
A one-to-one mapping of IP addresses that allows a user to map an IP address on an internal network to an IP address that is to be made public. If static NAT is used, traffic can be initiated from either side of the connection. See also network address translation.
static paging
A phase of the IPL sequence that takes place prior to limited paging during which only predefined areas of the load-source disk unit can be accessed. See also full paging, limited paging, prestatic paging.
subnet mask
For internet subnetworking, a 32-bit mask used to identify the subnetwork address bits in the host portion of an IP address.
A group of four Power 775 CEC drawers that have a total of 1024 processor cores in addition to the memory, hub switch chips, and PCIe slots.
switch leaf
See leaf.
symmetric multiprocessor (SMP)
A system in which functionally identical multiple processors are used in parallel, providing simple and efficient load balancing.
Synchronous Data Link Control (SDLC)
A protocol for managing synchronous information transfer over a data link connection.
A computer and its associated devices and programs.
system ASP
The auxiliary storage pool where system programs and system data reside. It can also include user programs and user data. The system ASP (ASP1) always exists. See also auxiliary storage pool, user ASP.
system console
The device that is in control of the operating system after the system has been shut down and when the system is in a restricted state. Only one device can be the system console at one time. See also backup console.
system event log
A log file on the system that stores information about system problems and performance issues.
system firmware
See server firmware.
System i
A family of IBM systems distinguished by their object-oriented architecture, integrated relational database, and high-level machine interface. System i systems support the IBM i, i5/OS, Operating System/400, AIX, and Linux operating systems. See also i5/OS, IBM i.
System i Navigator
A no-charge feature of IBM System i Access for Windows that is bundled with the IBM i operating system. System i Navigator provides a graphical user interface to common System i management functions. Some of the common management functions include basic operations, TCP/IP configuration, job management, users and groups, database management, and Management Central.
system management services (SMS)
An interface that provides information about a system or logical partition and that performs tasks such as changing the boot list and setting the network parameters. This interface is used for AIX or Linux logical partitions.
System Manager Security
An application on the Hardware Management Console (HMC) that ensures that the HMC can operate securely in the client/server mode.
system port
A serial port that is available for specifically supported functions. This port is limited to serial-connected TTY console functions and use of approved call-home modems, and, in some cases, an uninterruptible power supply.
system power control network (SPCN)
An asynchronous serial communications network. SPCN connects the power system in participating components to the operating system and can report critical changes and power failures in those components to the operating system. SPCN gives the operating system control of electrical power.
system processor
The logic that contains the processor function to translate and process the operating system commands and application program commands.
system reference code (SRC)
An alphanumeric string of characters (code) that contains information, such as a failing field-replaceable unit, for a service representative, customer engineer, or customer to use for servicing a system.
system service tools (SST)
The part of the service function used to service the system while the operating system is running.
Systems Network Architecture (SNA)
The description of the logical structure, formats, protocols, and operational sequences for transmitting information through and controlling the configuration and operation of networks.
system unit
The part of a computer that contains the processing unit, and may contain devices such as disk units and tape units.


target server
  1. In upgrades, the planned hardware configuration and software level that exists when the upgrade is completed.
  2. A database that contains replication target tables.
See Transmission Control Protocol.
See Transmission Control Protocol/Internet Protocol.
In TCP/IP, a protocol that provides remote-terminal connection service. Telnet enables users of one host to log on to a remote host and interact as if they were directly attached terminal users of that host.
terminal type (tty)
A generic device driver for a text display. A tty typically performs input and output on a character-by-character basis.
Thin Console
An appliance that provides a 5250-based operating system console for the IBM i operating system. This appliance connects directly to the server using one of the HMC Ethernet ports (labeled HMC 1 and HMC 2) on the back of the server.
thin provisioning
The ability to define a storage unit (full system, storage pool, volume) with a logical capacity size that is larger than the physical capacity assigned to that storage unit.
A single web page at any level within an information center hierarchy.
topic collection
A functional group of web pages. A topic collection can be a grouping at any level within an information center hierarchy.
The physical or logical mapping of the location of networking components or nodes within a network. Common network topologies include bus, ring, star, and tree.
Transmission Control Protocol (TCP)
A communication protocol used in the Internet and in any network that follows the Internet Engineering Task Force (IETF) standards for internetwork protocol. TCP provides a reliable host-to-host protocol in packet-switched communication networks and in interconnected systems of such networks. See also Internet Protocol.
Transmission Control Protocol/Internet Protocol (TCP/IP)
An industry-standard, nonproprietary set of communication protocols that provides reliable end-to-end connections between applications over interconnected networks of different types.
A key database that holds signer certificates for only the target servers that the user trusts.
See terminal type.
twinaxial cable
A cable made of two twisted wires inside a shield.


See Universal Asynchronous Receiver/Transmitter.
See Unified Extensible Firmware Interface.
unattended mode IPL
An IPL mode that automatically loads the operating system without any user interaction. See also attended mode IPL.
uncapped partition
A logical partition that uses a shared processor pool whose assigned current processing capacity might be exceeded when the shared processor pool has any unused processing power. The value assigned to the uncapped partition determines the percentage of unused processing power that a logical partition receives when more than one uncapped partition is contending for the processing power in the shared processor pool.
uncapped weight
A number in the range of 0 through 255 that can be set for each logical partition in the shared processor pool. Based on these values, any available unused capacity is distributed to contending logical partitions in proportion to the normalized values of their uncapped weight.
Unified Extensible Firmware Interface (UEFI)
A specification that details the interface between the operating system and the platform firmware at boot time. It is not specific to any processor architecture.
uninterruptible power supply (UPS)
A source of power from a battery installed between the commercial power and the system that keeps the system running, if a commercial power failure occurs, until it can complete an orderly end to system processing.
The defined space within disk units that is addressed by the system.
Universal Asynchronous Receiver/Transmitter (UART)
An electronic circuit that transmits and receives data through a serial port.
Universal Serial Bus (USB)
A serial-interface standard for telephony and multimedia connections to personal computers.
To apply fixes to a system.
  1. To install a new version or release of a product to replace an earlier version or release of the same product.
  2. Any hardware or software change to a later release, or any hardware addition or software addition.
See uninterruptible power supply.
See Universal Serial Bus.
user ASP
  1. One or more auxiliary storage pools used to isolate journals, journal receivers, and save files from the other system objects stored in the system ASP. See also auxiliary storage pool, system ASP.
  2. One or more storage units used to isolate some objects from the other objects that are stored in the system ASP and other user ASPs. User ASPs are defined by the user.
user ID
See user identification.
user identification (user ID)
The name used to associate the user profile with a user when a user signs on to a system.


vary off
To make a device, control unit, or line unavailable for its normal intended use.
vary on
To make an independent disk pool available for its normal, intended use. All of the primary and secondary disk pools in a disk pool group will vary on together.
See vital product data.
See Virtual Ethernet Port Aggregator.
A separately licensed program that typically has significant new code or new function.
See Virtual I/O Server.
VIOS logical partition
A partition running the Virtual I/O Server (VIOS) software that facilitates the sharing of physical I/O resources between client logical partitions within a server.
Virtual Ethernet Port Aggregator (VEPA)
The capability of a physical server to collaborate with an adjacent bridge to provide frame relay services between multiple virtual machines, which are located on a server and also on the external network.
virtual Fibre Channel adapter
A virtual adapter that provides client logical partitions with a Fibre Channel connection to a storage area network through the Virtual I/O Server logical partition. The framework uses N_Port ID Virtualization (NPIV) and each virtual Fibre Channel adapter has a pair of unique Worldwide Port Names (WWPNs) associated with it.
Virtual I/O Server (VIOS)
Software that facilitates the sharing of physical I/O resources between client logical partitions within the server.
The substitution of virtual resources for actual resources, where the virtual resources have the same functions and external interfaces as their counterparts, but differ in attributes, such as size, performance, and cost. Virtualization is commonly applied to physical hardware resources by combining multiple physical resources into shared pools from which users receive virtual resources.
virtual local area network (VLAN)
A logical association of switch ports based upon a set of rules or criteria, such as Medium Access Control (MAC) addresses, protocols, network address, or multicast address. This concept permits the LAN to be segmented again without requiring physical rearrangement.
virtual private network (VPN)
An extension of a company intranet over the existing framework of either a public or private network. A VPN ensures that the data that is sent between the two endpoints of its connection remains secure.
virtual processor
A setting that defines the assigned processing capacity represented to the operating system. Virtual processors represent a processing capacity less than that of a physical processor. A logical partition in the shared processor pool must have at least as many virtual processors as its assigned processing capacity.
virtual SCSI client adapter
A virtual adapter in one logical partition that communicates with a virtual SCSI server adapter in another partition. A virtual SCSI client adapter allows a logical partition to access a storage device being made available by another logical partition. See also virtual SCSI server adapter.
virtual SCSI server adapter
An adapter in one logical partition that is available to a virtual SCSI client adapter in another logical partition. A logical partition to which a storage device is assigned can map that device to a virtual SCSI server adapter. See also virtual SCSI client adapter.
virtual server
A system composed of partitioned, shared, or virtualized resources presented from a host system. An operating system and other software can be installed on a virtual server. See also logical partition.
virtual server network (VSN)
The capability that provides enhanced access, security control, and integrated management for interconnected storage and virtual servers, and for interconnected fabrics, such as virtual switches and routers.
virtual service processor (VSP)
The firmware that controls the powering on and powering off of a logical partition, including loading the firmware that controls the I/O slots and initializing the memory space of the logical partition.
virtual terminal
A system object, created and controlled by an application program, that provides a functional representation or simulation of a physical display station.
Virtual Trusted Platform Module (VTPM)
A software implementation of the Trusted Platform Module specification that is described by the Trusted Computing Group. The Trusted Platform Module is implemented as a physical chip on systems.
vital product data (VDP, VPD)
Information that uniquely defines system, hardware, software, and microcode elements of a processing system.
See virtual local area network.
VLAN tagging
The process of adding a VLAN number to the Ethernet packet to logically segment a physical network, thereby restricting the network layer 2 connectivity to the members who belong to the same VLAN.
A commercially available, proprietary virtualization environment for System x and similar platforms.
voltage regulator module (VRM)
A replaceable module on a system board that regulates voltage to the microprocessor.
See vital product data.
See virtual private network.
See voltage regulator module.
See virtual server network.
See virtual service processor.
See Virtual Trusted Platform Module.


See World Wide Web.
A related collection of files available on the web that is managed by a single entity (an organization or an individual) and contains information in hypertext for its users. A website often includes hypertext links to other websites.
User assistance that is an alternate path usually through complex and infrequently performed tasks. Presented sequentially, the panels of the wizard prompt the user for responses, and then take that data and perform the task. Wizards complete a single task and are usually self-contained.
A terminal or personal computer at which a user can run applications and that is usually connected to a mainframe or a network. See also display station.
worldwide node name (WWNN)
A unique 64-bit identifier for a host containing a Fibre Channel port. See also worldwide port name.
worldwide port name (WWPN)
A unique 64-bit identifier associated with a Fibre Channel adapter port. The WWPN is assigned in an implementation-independent and protocol-independent manner. See also worldwide node name.
World Wide Web (web, WWW)
A network of servers that contain programs and files. Many of the files contain hypertext links to other documents available through the network.
See worldwide node name.
See worldwide port name.
See World Wide Web.

Last updated: Fri, June 16, 2017