Why does one of my Sysview PMO for DB2 for z/OS Data Collectors have the following message repeated over and over again? "GSS ERROR: Invalid PLIST, "GSST" is missing IMOD ERROR RETURN CODE 20 REASON 31 "

Document ID : KB000012172
Last Modified Date : 14/02/2018
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Introduction:

Using the GSS interface with CA Sysview Performance Monitor Option for DB2 for z/OS (IDB2).

Question:

Why are we seeing a lot of the message GSS ERROR: Invalid PLIST, "GSST" is missing IMOD ERROR RETURN CODE 20 REASON 31 in the

CA Sysview PMO for DB2 for z/OS (IDB2) joblog?

This seems to only be occurring on the IDB2 Data Collector that monitors a heavily used DB2 subsystem.

Answer:

The 'IMOD ERROR RETURN CODE 20 REASON 31' indicates the GSS MAXXREQ table ran out of room to handle the volume of IMOD requests. 

To address this condition, increase the GSS runparm values for EVENTS and MAXXREQ to: EVENTS 32767 MAXXREQ 8000.

Also, you will want to make certain the GSS 14.0 ptf RO42823 is applied.