CNTLUNIT
Each physical control unit in the I/O configuration must be specified in a separate CNTLUNIT statement to be used. This requirement includes control units that reside in the same physical unit as an I/O device or in another control unit.
A CSS uses the control unit headers for queuing I/O requests for the devices attached to the associated physical control units. One I/O request queue exists for each control unit header. A CSS adds to the same I/O request queue all I/O requests for all devices in the control unit header. (Devices in the control unit header are all the devices attached to the set of physical control units that are in the control unit header.)
IOCP also establishes a rotation order for the channel paths associated with each control unit header. When initiating I/O requests associated with the control unit header, a CSS uses this rotation order to determine the sequence for selecting channel paths. See Rotation order for a description of how IOCP establishes the rotation order of the channel paths.
The CNTLUNIT statement must follow any CHPID statements that specify channel paths the control unit uses. The CNTLUNIT statement must precede any IODEVICE statements that refer to the control unit.
See Coding IOCP statements for a summary of the rules for coding statements and the notation used in this document to illustrate statements.
[symbol] CNTLUNIT CUNUMBR=number
PATH=((CSS(cssid),chpid[,chpid]...),...)
[LINK=((CSS(cssid),link address
[,link address]...),...)]
[CUADD=address]
[PROTOCL={D|S|S4}]
SHARED={Y|N}
UNIT=type
UNITADD=((address[,number]),...)
- CUNUMBR=number
- Specifies the hexadecimal number that is assigned to the control unit. One to four hexadecimal digits in the range of 0000-FFFE can be specified. You must assign a unique number to each control unit. The numbers can be assigned arbitrarily.
- PATH=
-
- cssid
- Specifies the logical channel subsystem (CSS) IDs associated with this parameter. A CSS ID is a
1-digit number in the range 0-n. See Table 2 to determine
the maximum CSS ID your CPC supports.
The CSS IDs must have been defined in the PART or PARTITION keyword on the RESOURCE statement. You can specify as many CSSs as you defined. If only a single CSS was defined, the CSS parameter is optional.
- chpid
- Specifies the channel paths in each CSS that are attached to the control unit. You must specify
two hexadecimal digits for each channel path identifier (chpid) or two
asterisks (**). You cannot duplicate chpid numbers within a CSS. You can specify a maximum of eight chpids in a CSS. However, you can specify only one channel path in a CSS for:You can specify a maximum of seven pairs of asterisks in a CSS. Each pair of asterisks specifies that a managed path (CHPARM keyword) can be added to the control unit and identifies the control unit as being managed by dynamic CHPID management. The number of pairs of asterisks specifies the number of managed paths that can be added to the control unit. The following restrictions apply to a managed control unit:
A spanned channel path is not required to attach to a control unit from each CSS to which the channel path is assigned.
The channel paths attaching to the control unit must be all unshared or all shared. You cannot mix shared and unshared channel paths to a control unit. All spanned channel paths are also shared channel paths.You can assign a CNC, CTC, or FC channel path (TYPE keyword) to only one control unit unless one of the following statements is true:
You can assign a CFS, CFP, CBS, CBP, ICP, CIB, CL5, and CS5 channel path (TYPE keyword) to only one control unit. You cannot assign a CFR or CBR channel path (TYPE keyword) to a control unit. CFR and CBR channel paths do not require control units or devices.
You can assign an OSC, OSE, OSN, or FCP channel path (TYPE keyword) to only one control unit.You can assign an IQD, OSD, OSM, or OSX channel path (TYPE keyword) to only one control unit unless the control unit has a logical address (CUADD keyword). If you need to define more than 256 devices for an IQD channel path or 254 devices for an OSD, OSM, or OSX channel path, define multiple control units. Specify a unique logical address for each control unit using the CUADD keyword.
All channel path types (TYPE keyword) attaching to a control unit must meet the following restrictions:You can intermix FC channel paths with CNC and FCV channel paths. To ease migrating from ESCON channels to FICON channels using dynamic I/O configuration, mix FC channel paths with CNC and FCV channel paths. The mixture allows you to dynamically add FC channel paths to a control unit while keeping its devices operational. A second dynamic I/O configuration change can then remove the CNC and FCV channels while keeping the devices operational.
For some types of control units and devices, there might be small operational performance differences when intermixing (for example, Resource Measurement Facility (RMF) usage calculations and channel path reconnection). Dynamic CHPID management cannot manage a control unit that contains intermixing. For these control units and devices, mixing of FC channel paths with CNC and FCV channel paths should be temporary. Non-dynamic I/O users are recommended to avoid mixing these channel paths.
When mixing ICP, CIB, CL5, and CS5 channel paths in the same control unit, the CSYSTEM keyword value on the CIB, CL5, and CS5 (if specified) channel paths must be identical to the local system name of the CPC (LSYSTEM keyword). When mixing CIB, CL5, and CS5 channel paths in the same control unit, any CSYSTEM keyword values that are specified for the channel paths must be identical. If a CS5 or CL5 channel path did not specify a CSYSTEM keyword value, it is ignored.
Other types of control units and devices fully support this intermixing. To determine the level to which your control units and devices support intermixing, see their device planning manuals. For control units that support intermixing, consult their performance white papers for guidance on how to best configure channels from a performance perspective. To improve the balance of workload across channels in an intermixed environment, alternate ESCON (CNC and FCV) and FICON (FC) channel paths in the control unit header for this control unit. Use the following patterns:
- LINK=
-
- cssid
- Specifies the logical channel subsystem (CSS) IDs associated with this parameter. A CSS ID is a
1-digit number in the range 0-n. See Table 2 to determine
the maximum CSS ID your CPC supports.
Each CSS ID must have been specified in the PATH keyword for this control unit. You can specify as many CSSs as you specified in the PATH keyword. If only a single CSS was specified in the PATH keyword, the CSS parameter is optional.
- link address
- Specifies the link addresses to which the control unit is attached. The order in which the link
addresses are specified for each CSS corresponds to the order in which the channel paths are
specified in the CSS parameters of the PATH keyword. For example, the second link address identified
for CSS 1 in the LINK keyword corresponds to the second channel path identified for CSS 1 in the
PATH keyword.
The LINK keyword is optional if none of the channel paths in the PATH keyword attach to an ESCON or FICON Director (SWITCH keyword). You do not need to specify link addresses for a CSS if none of the channel paths specified for the same CSS ID in the PATH keyword attaches to an ESCON or FICON Director. You can specify two or four asterisks for link addresses that correspond to channel paths not attached to a director. For ESCON channel paths not attached to a director, specify any valid link address values.
FC channel paths not attaching to a director can specify only link addresses of asterisks. A link address of asterisks must be specified for each channel path in the PATH keyword that is specified as two asterisks (**). This pairing of asterisks in the PATH and LINK keywords of the CNTLUNIT statement indicates the number of managed paths (CHPARM keyword) that can be added to the control unit.You must specify link addresses with two or four hexadecimal digits. The valid link address range is 01-FE for CBY, CVC, CNC, CTC, and FCV channel paths (TYPE keyword). The valid link address range is 0000-FFFF for an FC channel path. To determine whether to specify a 2- or 4-digit link address for an FC channel path and how to select a 4-digit link address, see Defining FICON switch configurations. When you specify a 4-digit link address for an FC channel path, every link address for that channel path must also be four digits.
If you specify the LINK keyword for a CSS, you must specify either a valid link address or asterisks for every channel path in the same CSS in the PATH keyword. If you do not specify the LINK keyword or specify asterisks, IOCP assumes that the link address is arbitrary and assigns a link address of 0D. Link addresses specified in the LINK keyword for dynamic connections through a director must equal the link addresses associated with the physical ports on the director to which the control unit is attached. However, link addresses specified for channel paths having dedicated connections through an ESCON Director can be arbitrary.For channel paths having dedicated connections through an ESCON Director, specify the corresponding link address on the CNTLUNIT statement as the link address associated with the physical port on the ESCON Director to which the control unit is attached. If a CTC channel path does not attach to an ESCON Director or has a dedicated connection through an ESCON Director, the link address specified here might not be the link address the CSS uses.
For maximum availability of a control unit and its devices, see List of I/O devices and control units for recommendations for selecting the physical ports on an ESCON Director to attach to the control unit.
The LINK keyword is valid only for CBY, CVC, CNC, CTC, FCV, and FC channel paths (TYPE keyword).
Even though you can specify multiple link addresses for CBY and CVC channel paths (TYPE keyword), the I/O subsystem does not support dynamic connections through an ESCON Director for CBY or CVC channel paths. A CBY or CVC channel path that attaches to an ESCON Director can have only a dedicated connection through it. Therefore, you can connect only one link address on an ESCON Director to a CBY or CVC channel path at a time.
Note: If you specify no link address for a channel path that does not attach to a director, IOCP selects a link address of 0D to address the control units on the channel path. This arbitrary link address is displayed by the I/O Problem Determination (IOPD) frame and the IOCDS Display frame on the Support Element. However, the IOCP reports show that no link address was specified on its CNTLUNIT statements.The I/O subsystem flags a channel path with a definition error in the following situations:In these three instances, the channel path is unavailable and remains so until the error is resolved.
In addition to the preceding syntax rules, the following configuration rules also apply when specifying link addresses. For link addresses with four digits, rules are enforced against the switch to which the channel path is connected (that is, the entry switch) rather than the switch to which the control unit is attached. When a 4-digit link address is specified for a channel path, specify four-digit link addresses for all paths that have the same entry switch. Otherwise, IOCP cannot enforce some of the following switch configuration rules.
- FC control unit definition considerations:
-
FC channel paths (TYPE keyword) support a maximum number of unit address ranges and unit addresses. (See Table 1.) IOCP calculates the number of unit address ranges and unit addresses for a spanned FC channel path (PATH keyword in the CHPID statement) as follows:
For example, CHPID 10 is an FC channel path that is spanned to CSSs 0, 1, 2, and 3. It is assigned to a control unit in CSSs 0, 1, and 3. The channel path uses link address C0 in CSSs 0 and 1 and link address D0 in CSS 3. Because there are a total of two unique link addresses, two unit address ranges are counted. If the UNITADD keyword specified 128 unit addresses, a total of 256 unit addresses are counted.
- CUADD=address
- Specifies the logical address for the
control unit.
For example, the IBM Enterprise Storage Server® (ESS) 2105 control unit requires that the logical address specified with the CUADD keyword matches the control unit image address associated with the corresponding control unit logical subsystem (LSS).
Note: Not all ESCON and FICON control units support logical addressing.The address is 1-2 hexadecimal digits in the range 0-F for CNC, CTC, and FCV channel paths and in the range 00-FF for FC, IQD, OSD, OSM, and OSX channel paths. However, if FC channel paths are mixed with CNC or FCV channel paths, the address must be in the range 0-F. The address allows you to specify a CNC, CTC, FCV, or FC channel path on multiple CNTLUNIT statements for a given path (pchid.link or switch.link) or to specify an IQD, OSD, OSM, or OSX channel path on multiple CNTLUNIT statements.Note: A CNC or CTC channel path not assigned to an ESCON Director is viewed as having a single link address.The CUADD keyword is valid only for: CNC, CTC, FCV, FC, IQD, OSD, OSM, and OSX channel paths (TYPE keyword).
For a channel path assigned to an ESCON CTC or FICON CTC control unit, the logical address identifies the logical partition to which this channel path is to communicate. If the remote channel path to which this channel path must communicate is not shared, then the logical address must be zero or not specified. If the remote channel path to which this channel path must communicate is shared, then the logical address must equal the wanted MIF image ID1 from the RESOURCE statement for the logical partition that the shared channel path can access. This applies to CNC, CTC, FCV, and FC remote channel paths that are shared.
However, if the remote channel path is a shared FC channel path on a CPC that supports multiple logical channel subsystems (that is, if the IOCP described in this document supports the CPC), then the logical address must equal the combination of the wanted CSS ID and the MIF image ID for the logical partition with which you want to communicate. For example, if the remote channel path is shared within CSS 1 and you want to communicate with the logical partition that has MIF image ID 5, specify CUADD=15.
ESCON CTC and FICON CTC communications are on a logical partition basis even if a channel path is shared by multiple logical partitions. You must define a control unit for every logical partition to which you want to communicate.
Note: The preceding CTC requirements for the CUADD keyword apply to any type of remote CPC (for example, a 9672 CPC).For more information about ESCON CTC and FICON CTC communication, see ESCON and FICON Channel-to-Channel Reference, SB10-7034.
In addition to the preceding syntax rules, the following configuration rules also apply when specifying the CUADD keyword:Otherwise, the combination switch.link.cuadd is allowed only once in the configuration.
- PROTOCL=
- Specifies
the interface protocol that the parallel control unit uses when operating
with the channel paths specified in the PATH parameter. The PROTOCL
keyword is meaningful only for CVC channel paths (TYPE keyword). IOCP
ignores the PROTOCL keyword for all other channel path types. IOCP
assigns PROTOCL=D to control units attached to CBY channel paths.
Note: Incorrect specification of the PROTOCL parameter might produce unpredictable results. For example, if you specify PROTOCL=S (data streaming) for a control unit that supports the DC interlock protocol, I/O requests can result in detected errors (such as data overruns or interface control checks) or in undetected errors. Additionally, specifying PROTOCL=S for a control unit that runs at a maximum data rate of 4.5 MB per second could cause bus parity checks.
- D
- Specifies the direct-coupled interlock (DC interlock) protocol. This protocol is the standard I/O interface that requires a response to a demand. If you do not code PROTOCL, D is the default.
- S
- Specifies data streaming protocol at a maximum data rate of 3.0 mps (megabytes per second). This protocol does not require the demand response but continues at the rate governed by the control unit.
- S4
- Specifies data streaming protocol at a maximum data rate of 4.5 mps. This protocol does not require the demand response but continues at the rate governed by the control unit.
- Specifies the level of concurrency of
I/O requests that the parallel channel path allows for the control unit. IOCP automatically sets the
control unit type (1 or 2) based on the SHARED parameter that you specify. See List of I/O devices and control units for more information about specifying
the SHARED parameter. (For further information about control unit types, see Control unit types.)
The SHARED keyword is meaningful only for CVC channel paths (TYPE keyword). IOCP ignores the SHARED keyword for all other channel path types. Control units that attach to CBY, CNC, CTC, FCV, FC, FCP, IQD, OSC, OSD, OSE, OSM, OSN, or OSX channel paths are type 2. Control units that attach to CFS, CFP, CBS, CBP, CIB, CL5, CS5, and ICP channel paths are type 1.
- Y
- Specifies that the
control unit supports:
IOCP assigns the control unit as type 1.
The channel ensures that only one I/O request is processed at a time for all devices sharing the control unit. If sense information is pending in the control unit for an I/O device attached to the control unit, the channel ensures that I/O requests for other I/O devices attached to the control unit are not initiated until the system control program has issued an I/O request to clear the pending sense information.
- N
- Specifies that the control unit supports multiple I/O requests concurrently (one for each attached I/O device). IOCP assigns the control unit as type 2. Specifying SHARED=N for a control unit that does not support multiple concurrent requests can result in a control unit malfunction.
- UNIT=type
- Specifies the type of control unit. You
can specify as many as eight alphanumeric or special (-, #, @, or $) characters that identify the
type of control unit. IOCP checks the syntax for alphanumeric or special characters.
IOCP takes special actions for control unit types SCTC and FCTC. See the LINK and CUADD keyword sections for the CNTLUNIT statement. Also, control unit type FCTC is valid only for FC channel paths (TYPE keyword).
You must specify a type for every control unit in your I/O configuration.
A Server Time Protocol (UNIT=STP) control unit with CIB, CL5, or CS5 channel paths (TYPE keyword) must have only external connections. No CIB, CL5, or CS5 channel path in an STP control unit can have a CSYSTEM keyword value that matches the local system name (LSYSTEM keyword) of the CPC, forming an internal connection. Also, an STP control unit cannot have ICP channel paths.
Notes: - UNITADD=
-
- address
- Specifies the unit addresses of the I/O devices that the control unit recognizes. You specify two hexadecimal digits in the range of 00-FF. For example, UNITADD=((0A),(0B),(0F)) specifies that the control unit recognizes unit addresses 0A, 0B, and 0F. At least one unit address must be specified. A unit address does not need to represent an attached device.
- number
- Specifies the number of sequential unit addresses the control unit recognizes. You specify a 1-, 2-, or 3-digit decimal value in the range of 1-256. For example, UNITADD=((0A,3)) indicates that the control unit recognizes unit addresses 0A, 0B, and 0C. The unit address plus the number of addresses must not exceed an address of FF. If the number is omitted, a value of 1 is assumed.
You can specify a maximum of eight addresses or sets of address and number values for parallel control units. For ESCON or FICON control units, you can specify only one range of unit addresses. The unit addresses specified for the CNTLUNIT statement must include the unit addresses of the attached devices. The unit address of a device is taken from the UNITADD parameter of the IODEVICE statement if specified or from the rightmost two digits of the device number specified with the ADDRESS parameter of the IODEVICE statement.Note: See List of I/O devices and control units for some exceptions and recommendations that apply to specific device types. Some ESCON and FICON control units require unit address range to begin with (hexadecimal) 00.IOCP ignores the UNITADD keyword for control units attached to CFS, CFP, CBS, CBP, CIB, CL5, CS5, FCP, ICP, IQD, OSC, OSD, OSE, OSM, OSN, or OSX channel paths. IOCP defines unit addresses 00-FE for control units attached to OSD, OSE, OSM, OSN, or OSX channel paths. IOCP defines unit addresses 00-FD for control units attached to FCP or OSC channel paths. IOCP defines unit addresses 00-FF for control units attached to IQD channel paths.
The full range of unit addresses that the control unit can address must be specified regardless of whether devices are attached. If you do not specify one or more of the unit addresses that the control unit can address, missing interruption handler (MIH) situations result. However, this requirement does not apply to ESCON CTC or FICON CTC control units.Notes:A shared CTC channel path (SHARED keyword specified in the CHPID statement) can generate more unit addresses and unit address ranges than an unshared channel path. See Shared ESCON CTC considerations.
A spanned FC channel path (PATH keyword in the CHPID statement) can generate more unit addresses and unit address ranges than an unspanned channel path. See "FC control unit definition considerations" on page FC control unit definition considerations:.