A form of fast write where the data is written concurrently to cache and nonvolatile storage,
and is destaged to DASD when buffer space is needed or by operator-initiated command.
database ID (DBI)
The ECB field that identifies which subsystem
and subsystem user databases are being used by a particular entry control block (ECB).
The logical or relative record number of a record in a database.
database reorganization (DBR)
The process whereby the user captures all or selected fixed file and pool records from one
system and reloads them on a different or reconfigured system.
data collection programs
The online programs that collect the system activity data used to analyze system
performance.
Data collection/reduction
The z/TPF utility used to tune the system and
manage the sensitive balance between utilization of resources and response to the users. See
data collection programs and data reduction programs.
data definition
In z/TPF collection support (z/TPFCS), a list of characteristics that are assigned to a
collection when the collection is created. The characteristics include record IDs, shadowing, and
collection lifetime.
A data definition describes a data object and reserves storage. A data definition can also
provide an initial value. Definitions appear outside a function or at the beginning of a block
statement.
data element
A unit of storage in a data entry for a coupling facility (CF).
See also data entry.
Data Encryption Standard (DES)
In symmetric cryptography, a cryptographic algorithm designed to encrypt and decrypt data using
a 64-bit (of which only 56 bits are used) key as specified in the Federal Information Processing
Standard 46, January 15, 1977. See cryptographic
algorithm.
data entry
A part of a list entry that holds user-defined data in a coupling facility (CF). A data entry contains units of storage called data
elements. See also data element and list entry.
A control block that is dynamically allocated from the private area of the entry control block (ECB). A DECB is a logical extension of an ECB and ECB data levels, and is used like a data level in
FIND/FILE processing. A DECB is not related to a data event. See also entry control block (ECB) and ECB data levels.
data event record
A logical set of data that was created, updated, or deleted and contains the modified data that
is collected as part of a user exit data event. For example,
a data event record consists of one or more logical
records (LRECs) from a single z/TPFDF subfile. See alsodata event and user exit data event.
datagram
In TCP/IP, the basic unit of information
passed across the Internet environment. A datagram contains a source and destination address along
with the data. An Internet Protocol (IP) datagram consists of an IP
header followed by the transport layer data.
In a CMC configuration, a type 5 host node that is dedicated to processing applications and does
not control network resources, except for its channel-attached devices. Synonymous with data host.
data link control (DLC)
The SNA protocols that initiate, control, check, and stop data transfer over a data link between
2 adjacent nodes.
data loader
The program that loads pilot tape data onto the online modules.
data loss exposure
A term describing the potential for a fast write data loss condition. An exposure exists as long
as there is fast write data in the cache for a device attached to a 3990 caching control unit with
the record cache subsystem RPQ.
data macro
A declarative macro that generates dummy control sections (DSECT)s defining records that may be
called by any z/TPF source program by using the
data macro name.
data record
A pool record where the actual data elements for the collection are stored. A data record often
contains more than one data element for a given collection.
data record information library (DRIL)
A file, used by the system test compiler (STC), containing an entry for all system data records
and message formats.
data reduction programs
The offline programs that process data collection records stored on the data collection tape to
generate the reports required for system performance analysis.
data store
A repository for persistent collections. A data store name is
subsystem-common, but the data in a data store is subsystem-unique.
data type
(1) A generic description of an elementary unit of information in a particular software system.
Common data types include whole numbers, decimal numbers, dollar amounts, dates, and text.
Higher-level data types may also be defined if abstract data types are supported. (2) A category
that specifies the interpretation of a data object such as its mathematical qualities and internal
representation.
DATXPAGE envelope
A record that serves as a package in which z/TPF collection support (z/TPFCS) stores all the other objects it wants
to file in that record.
DBF
A symbolic name, reserved to the z/TPF system, for a
general tape denoting the database reorganization capture tape for fixed files.
DBI
Database ID.
DBON
Database ordinal number.
DBP
A symbolic name, reserved to the z/TPF system, for a
general tape denoting the database reorganization capture tape for pool files.
DBR
Database reorganization.
DBRM
Database request module.
DCL
Dispatch control list.
DCR
Dispatch control record.
DDR
Dynamic device reconfiguration.
deactivate
The process by which all programs in a particular active E-type loader loadset become inactive.
deactivate function
The E-type loader function that prevents new
entry control blocks (ECBs) from entering the programs contained in specified
loadsets.
dead-letter queue (DLQ)
A queue to which a queue manager or application sends messages that it cannot deliver to their
correct destination.
DECB
Data event control block.
debug
To detect, locate, and correct mistakes in a program.
decrypt
In cryptography, to convert ciphertext into plaintext. Contrast with encrypt.
In computer security, the process of transforming encoded text or ciphertext into plaintext. See
ciphertext and plaintext.
dedicated resources
The resources owned by one processor in a loosely coupled complex. Dedicated resources are not
shared or switched to other processors. VFA is an example of this type of resource.
A virtual file access (VFA) attribute indicating that when an
application program issues a file-type macro, the record is copied to VFA, but the updated record is
not filed physically to DASD. The record is filed to DASD (1) when the record ages out, (2) when the
record is force filed, (3) when the system is cycling down from NORM state or cycling up after a
ZRIPL command is entered with the BP parameter specified, (4) when a catastrophic system error
results from a software IPL, or (5) when the ZVFAC DISABLE command is entered. Contrast with
immediate filing.
deployment descriptor
A file that contains configuration information for a specific capability in the z/TPF system. The file represents a valid instance of a
deployment descriptor schema. There are two mechanisms that are used
to manage deployment descriptors: common deployment and web services.
DES
Data Encryption Standard.
destage
The asynchronous writing of new or updated data from cache or nonvolatile storage to DASD.
device level selection enhanced (DLSE)
A DASD function available with 3390 emulated DASD. With DLSE, a DASD string can be attached to 4
storage paths on a DASD control unit. Using this configuration, as many as 4 devices on the same
DASD string can read or write data simultaneously.
device type
A z/TPF device that represents distinct
characteristics for accessing and managing the location of data on the online DASD subsystem. As
many as 4 physically different device types (DEVA, DEVB, DEVC, and DEVD) can be used in a z/TPF system.
DFAD
FACE driver.
DFW
DASD fast write.
DFW attribute
A user-specified caching attribute that allows a data record to be written as DASD fast write
data. Access to data with this attribute has performance benefits for both read and write
operations. This attribute is specified for a given record ID through the RIAT.
diagnostic output formatter (DOF)
The programs that convert the system error data on RTA tapes and RTL tapes into readable dump
listings used for debugging purposes.
digital certificate
A form of personal identification that can be verified electronically. Only the certificate
owner who holds the corresponding private key can present a certificate for authentication when
starting an SSL session. See certificate,
private key, and authentication.
digital signature
Information whose message digest is encrypted with an entity's private key and is appended to a
message to assure the recipient of the authenticity and integrity of the message. The digital
signature proves that the message was signed by the entity that owns, or has access to, the private
key. See private key.
direct attachment support
The support of a computer console directly attached to a subchannel.
directional capability
The capability of data flow on a communication line: simplex transmissions flow in one
direction; half-duplex transmissions flow in either direction at a time; full-duplex transmissions
flow in both directions simultaneously.
directory
In coupling facility (CF) cache support, a directory for the CF cache structure where the z/TPF system keeps control information about data shared among
cache users. The directory contains one directory entry for each piece of data that users
share.
directory entry
A field with two formats. The first format is used mainly to contain the file addresses of both
the primary as well as the shadow copy of a record. The second format contains the next available
relative record number (RRN) that z/TPF collection support (z/TPFCS) will use for the associated collection.
directory-only cache
A coupling facility (CF) cache structure that contains directory entries
but no pieces of shared data. Directory-only cache users do not store data in the CF cache structure. The directory-only users use the CF cache structure to maintain the consistency of data in their
local caches.
directory record
A special type of pool record used to store directory entries.
directory reordering
The storage management process that retrieves a new pool directory set when the pool directory
set currently in use is nearly depleted.
dirty-read cursor
A nonlocking type of cursor for read-only operations.
disk formatter
An offline program used to format a disk module to z/TPF system requirements.
disk pack initialization
The system initialization process that checks the tracks assigned to each disk pack and
initializes the necessary volume labels.
dispatch control list (DCL)
The 3rd-level record in the centralized list handling (CLH) routines. There is 1 DCL for each
CPU loop list; it contains the addresses of work items to be dispatched.
dispatch control record (DCR)
The 2nd-level record in the centralized list handling (CLH) routines. There is 1 DCR for each
CPU loop list. This record contains a pointer to the DCL as well as status information for that
list.
dispatch management table (DMT)
The 1st-level record in the centralized list handling (CLH) routines. There is 1 such record in
a system. This record contains pointers to the 2nd-level information for each of the CPU loop list
types in the system.
dispense mode
In a file address compute program (FACE) table that supports
FARF3/FARF4 addresses or FARF4/FARF5 addresses, the file address format (FARF3, FARF4, or FARF5)
that is returned to you when the system requests a file address.
distinguished name (DN)
In computer security, the name and address of the person and organization to whom a certificate
has been issued. See certificate.
DLC
Data link control.
DLSE
Device level selection enhanced.
DMT
Dispatch management table.
DN
Distinguished name.
DOBT
Dynamic override bitmap table.
DOF
Diagnostic output formatter.
dormant subsystem user
A subsystem user that was included at initialization but has been deactivated because of an
unsuccessful global load. A dormant subsystem user cannot be reactivated without reinitializing the
system.
DOT
Dump override table.
DRIL
Data record information library.
dump buffer area
A storage area that is used to hold system error dumps before they are written to tape.
dump group
A group of programs (BAL or C shared object) that is
associated with specific areas of the z/TPF system. When
a system error occurs in any program in the dump group, the associated areas are included in the
dump. Use the loader attribute card or the ZAPAT command to assign programs to a dump group. Use the
ZIDOT command and the IDOTB macro to define the areas to be dumped for a specific dump group.
dump override table (DOT)
A table containing both the static override bitmap table (SOBT) and the dynamic override bitmap
table (DOBT). These tables contain information that determines which large storage areas are to be
included in dumps for particular system errors.
duplicate module
In a fully duplicated system or a partially duplicated system, the disk module that contains the
duplicate copies of records from the corresponding prime module.
duplicate record
When DASD records are duplicated, the two copies of a data record are called the duplicate
record and the primary record. Synonymous with backup
record.
dynamic device reconfiguration (DDR)
The process of recovering the contents of a tape control unit buffer so that the data can be
written to a new tape.
dynamic linkage
As part of z/TPF enter/back services, the
control program routine that resolves function calls and other external references between shared
objects. See also shared object.
dynamic LU resource
A remote LU resource that is defined to the z/TPF system using dynamic LU support.
dynamic LU support
Support that enables the z/TPF system to
automatically create resource definitions for new remote LU resources and new ALS resources.
dynamic override bitmap table (DOBT)
A table containing dump override bitmaps used to override the static override bitmap table.
Entries in the DOBT are created by the ZIDOT command.