Limiting CSM storage utilization

CSM storage limits are located in the SYS1.PARMLIB member IVTPRM00. The values you can allocate are:

ECSA MAX - the maximum amount of ECSA storage that CSM can allocate.
FIXED MAX - the maximum amount of fixed storage that CSM can allocate. This includes fixed CSM ECSA, CSM data space storage, and high virtual common (HVCOMM) storage above the 2 GB bar.
HVCOMM MAX - the maximum amount of HVCOMM storage that CSM can allocate.

If you do not specify values in the IVTPRM00 parmlib member, the system uses the default values of 100M ECSA, Start of change 512M FIXED End of change , and 2000M HVCOMM. You can change these values dynamically with the MODIFY CSM command. If the limit specified by these values is reached, results are unpredictable. TCP/IP might not be able to continue. IVTxxxx messages will be issued if CSM is unable to obtain storage. See z/OS MVS Initialization and Tuning Reference for additional information about the IVTPRM00 parmlib member.

To change your CSM settings dynamically, issue the following command:

MODIFY net,CSM,ECSA=value,FIXED=value,HVCOMM=value

where the ECSA value is in the range 1024 KB - 2048 MB, the FIXED value is in the range 1024 KB - 30720 MB, and the HVCOMM value is in the range 100 MB - 999999 MB. Additional information regarding the MODIFY command for CSM can be found in z/OS Communications Server: SNA Operation.