Not able to get into Sysview Performance Monitor for Db2 for z/OS (IDB2) due to USER SESSION FAILED RC=12

Products

• SYSVIEW Performance Management Option for DB2 for z/OS

Issue/Introduction

After upgrading a test Db2 subsystem cannot get into Sysview Performance Monitor for Db2 for z/OS (IDB2) from the Db2 tools for z/OS
Main Menu. Selecting 'IS' for Sysview Performance Monitor for Db2 for z/OS (IDB2) from the Db2 tools main menu receive message: 

SYSVIEW FOR DB2 USER SESSION FAILED WITH RC=12 ENSURE THE POST INSTALL STEPS HAVE BEEN COMPLETED BEFORE INVOKING THE USER INTERFACE.

Cause

Maintenance had been applied to the Db2 tools and the propagation of the SMP/E Target libraries to the Db2 tools 
Runtime libraries caused the previously modified IDB2 CLIST (from the Post Install process) to be overlaid with
 a 'vanilla' unedited version, thus the cause of the error message. 

Resolution

A backup copy of the edited IDB2 clist was copied into the Db2 tools runtime clist (CDBACLS0) library.