The first CV startup after upgrading IDMS from a previous release fails with a U3964 abend.
The error could occur at any stage during the startup and there are no other error messages to indicate a problem.
A common problem causing a U3964 abend after an upgrade is an insufficient stack size defined in the SYSGEN. The STACKSIZE is defined in the SYSTEM statement of the SYSGEN. Informational APAR GI76847 recommends you have a STACKSIZE of at least 3000 in the SYSTEM statement. You can make this change by running RHDCSGEN in batch with the following input statements:
MOD SYSTEM nnnn STACKSIZE 3000.