There are a few ways to approach this. The best place to get started is to get a heapdump from the Java JVM that IM is running. JSTACK is a pretty good tool to get this output. Basically, you'll end up with a snapshot of all of the memory and threads in your application server.
Then use the IBM Memory Analyzer Tool to examine the heap. What you're looking for is high memory usage by specific IM classes, and then you can focus on what the bottleneck may be.
JSTACK tips and tricks are here:
How to take Thread Dumps from a JVM
IBM Memory Analyzer Tool is here:
developerWorks : IBM Monitoring and Diagnostic Tools for Java - Memory Analyzer Version 1.4
CA Support is happy to help you analyze the heap dumps.
There are two common types of IM performance issues.
The first is due to poor role rule evaluations. This will be the case if the logins take a very long time before displaying a user's tasks in the IM User Console. This is the link for our documentation on optimizing role evaluations.
Performance and Optimization - CA Identity Manager - 12.6.5 - CA Wiki
The second type is due to an enormous number of users in the task persistence database tables. To avoid this, garbage collection should scheduled on a regular basis.
Cleanup Submitted Tasks - CA Identity Manager - 12.6.5 - CA Wiki
Please let me know if this sheds any light on the issue and don't hesitate to open a new support ticket to address this.
W.