When trying to generate a certificate the following error is received:
CAS2420E Could not perform key generation initialization RC:08, RSN:04, E-RC:00
The Top Secret Region size is too small.
Release: TOPSEC00200-15-Top Secret-Security
The most common fix is to make the region size, REGION=OM, but you can pick a specific size.
Make sure it is considerably larger than what you have to allow for command processing and growth.
You will have to recycle Top Secret to pull in the new region size but it only takes about a minute or less to stop TSS and then Restart.