CSM installation and definition

CSM is shipped and installed with the VTAM® product tape. However, many CSM functions are independent of VTAM. CSM storage limits and tuning parameters are defined in the CSM parmlib member, IVTPRM00.

The first two lines in the CSM parmlib member define the maximum amount of storage to be dedicated to fixed and ECSA buffers in CSM. You can also specify one POOL definition for each CSM buffer pool of a particular bufsize and bufsource combination. On each POOL definition, you can specify:

The minimum number of buffers to be free in the pool at any time (MINFREE). The storage pool is expanded when the number of free buffers falls below this limit.
The number of buffers by which the pool is expanded (EXPBUF) when the number of free buffers falls below MINFREE.
The initial number of buffers to be created in the pool (INITBUF). The pool does not contract below the contraction threshold value. CSM determines the contraction threshold value using the following formula:
MAX(INITBUF,(MINFREE+(2*EXPBUF)))

If parameters are not provided for a given CSM buffer pool, the IBM-supplied default values are used unless an application has provided these values on a IVTCSM REQUEST=CREATE_POOL macro.

See z/OS Communications Server: New Function Summary for a complete description of the CSM parmlib member.

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 and ECSA buffers in CSM. For more details about IBM Health Checker for z/OS, see z/OS Communications Server: SNA Diagnosis Vol 1, Techniques and Procedures.