SECCACHE is driven every time a logon is driven in your LPAR.
By caching the content of a user security record we can be more efficient each time the user performs a subsequent logon by eliminating the need to queue the TSS address space and potentially perform security file I/O.
The longer a user's security record remains active in the cache the better overall logon performance is achieved.
When either the cache index or data areas approach and reach the full warning percentage, CA Top Secret will automatically clear out entries that have not been used recently based on the expiration hours interval. This happens during TSS address space timer cycles (control option TIMER(xx) value). If this cleansing process drops the in use percentage back down below the warning level then no console messages are generated. If the process cannot get the percentage below the warning level then CA Top Secret will issue the console messages. That should always be an indication to review your SECCACHE configuration for tuning.