The MINFREE, INITBUF, and EXPBUF specifications in the CSM parmlib member, IVTPRM00, determine CSM buffer pools expansion and contraction. If these values are not specified in the CSM parmlib member, or if CSM cannot read that parmlib member during initialization, CSM uses the values specified by the application on the IVTCSM REQUEST=CREATE_POOL macroinstruction. If buffer pool tuning specifications are not available from either the CSM parmlib member or application request, system defaults are used.

This section describes how CSM buffer pool expansion and contraction are performed based on application settings. For more information about the CSM parmlib member, see the z/OS Communications Server: New Function Summary.