Parmlib member for communications storage manager (CSM)
Starting in z/OS® V2R2 Communications Server, communications storage manager (CSM) supports storage above the 64-bit address bar.
The IVTPRM00 parmlib member sets parameters for CSM storage. IVTPRM00 is read during CSM initialization as a result of the first issuance of the IVTCSM REQUEST=CREATE_POOL macro. (z/OS Communications Server issues this macro when started.) These definitions can also be changed without requiring a re-IPL by editing the IVTPRM00 member and issuing the MODIFY CSM command without specifying the parameters on the command.
- A data set defined by the PARMLIB DD statement in the TSO start procedure
- A data set in the logical parmlib concatenation
- SYS1.PARMLIB
IVTPRM00 has this format:
column |...+....1....+....2....+....3....+....4....+... FIXED MAX(maxfixK|M) ECSA MAX(maxecsaK|M) HVCOMM MAX(maxhvcommM) [POOL(bufsize, bufsource, initbuf, minfree, expbuf)]- Each line in IVTPRM00 must start in column one.
- FIXED and MAX or ECSA and MAX keywords must be separated by one or more spaces. It must be completed with its values on the same line.
The first three lines in the CSM parmlib member define the maximum amount of storage to be dedicated to fixed, ECSA, and HVCOMM buffers in CSM. Note that the fixed maximum represents the total fixed storage above and below the 2 GB bar. You can also specify one POOL definition for each CSM buffer pool of a particular bufsize and bufsource combination. If parameters are not provided for a given CSM buffer pool, the IBM®-supplied default values are used unless a program has provided these values on an IVTCSM REQUEST=CREATE_POOL macro.
- maxfix
- A decimal integer specifying the maximum bytes of fixed storage to be dedicated for use by CSM. The range is from 1024 KB to 30720 MB. The default value is 200 MB.
- maxecsa
- A decimal integer specifying the maximum bytes of ECSA storage
to be dedicated for use by CSM. The range is from 1024 KB to 2048
MB. The default is 100 MB. Restriction: The maxecsa value should be less than 90% of the ECSA available on the z/OS system. CSM adjusts the maxecsa value to 90% of the system ECSA value and issues the message IVT5590I when the maxecsa value configured is larger than 90% of the ECSA available on the system.
- maxhvcomm
- A decimal integer specifying the maximum bytes of HVCOMM storage to be dedicated for use by CSM. The range is from 100 MB to 999999 MB. The default value is 2000 MB.
- KB
- Denotes size in kilobytes
- MB
- Denotes size in megabytes.
- bufsize
- Specifies the size of the buffers in the pool to be created. Valid pool sizes are 4 KB, 16 KB, 32 KB, 60 KB, and 180 KB. bufsize is required for each POOL definition.
- bufsource
- Specifies the storage source from which buffers are allocated.
The values for bufsource are:
- ECSA
- Buffers are allocated from ECSA storage.
- DSPACE
- Buffers are allocated from data space storage.
- HVCOMM
- Buffers are allocated from high virtual common storage.
The bufsource variable is required for each POOL definition.
- expbuf
- Specifies the number of buffers by which the pool is expanded
when the number of free buffers falls below the minfree value. The valid ranges for each CSM buffer pool size are
as follows:
- Bufsize
- Range for Expbuf for ECSA and data space pools
- 4 KB
- 1 - 256
- 16 KB
- 1 - 256
- 32 KB
- 1 - 128
- 60 KB
- 1 - 68
- 180 KB
- 1 - 22
- Bufsize
- Range for Expbuf for HVCOMM pools
- 4 KB
- 1 - 1024
- 16 KB
- 1 - 512
- 32 KB
- 1 - 256
- 60 KB
- 1 - 136
- 180 KB
- 1 - 45
The expbuf variable is required for each POOL definition.
- initbuf
- Specifies the initial number of buffers to be created in the pool
when the first IVTCSM REQUEST=CREATE_POOL macro is issued by an application.
If this value is specified as 0, only the base pool structure is created.
In this case, the pool will be expanded on the first IVTCSM REQUEST=GET_BUFFER
based on the specification for expbuf. The
pool will not contract below the level specified by either initbuf or expbuf, whichever
is higher.
The range for initbuf is 0 - 9999. If initbuf is omitted, the IBM-supplied default value is used unless overridden by an application's CREATE_POOL request.
- minfree
- Specifies the minimum number of buffers to be free in the pool at any time. The storage pool will be expanded if the number of free buffers falls below this limit. The range for minfree is 0 - 9999. If minfree is omitted, the IBM-supplied default value is used unless overridden by an application's CREATE_POOL request.
Table 1 and Table 2 show the IBM-supplied default values for expbuf, initbuf, and minfree for the CSM buffer pools.
| Bufsize | 4 KB | 16 KB | 32 KB | 60 KB | 180 KB |
|---|---|---|---|---|---|
| EXPBUF | 16 | 8 | 4 | 4 | 2 |
| INITBUF | 64 | 32 | 16 | 16 | 2 |
| MINFREE | 8 | 4 | 2 | 2 | 1 |
| Bufsize | 4 KB | 16 KB | 32 KB | 60 KB | 180 KB |
|---|---|---|---|---|---|
| EXPBUF | 256 | 64 | 32 | 17 | 5 |
| INITBUF | 256 | 64 | 32 | 17 | 5 |
| MINFREE | 32 | 8 | 4 | 4 | 2 |
z/OS system symbols can be used in IVTPRM00. See z/OS Communications Server: SNA Network Implementation Guide for more information about this function.
IBM Health Checker for z/OS can be used to check whether appropriate values are defined for the maximum amount of storage to be dedicated to fixed buffers and ECSA buffers in CSM. For more details about IBM Health Checker for z/OS, see IBM Health Checker for z/OS: User's Guide.
| Task | Reference |
|---|---|
| Optionally update the IVTPRM00 parmlib member to specify the parameters to use when you allocate storage for CSM buffer use above the bar. | z/OS Communications Server: New Function Summary |
| Issue the D CSM command to monitor the use of storage above the bar that is managed by CSM. | z/OS Communications Server: SNA Operation |
| Issue the MODIFY CSM command to update values for storage above the bar that is managed by CSM. | z/OS Communications Server: SNA Operation |