Why does the number of cicsas processes decrease when RD.stanza has the minserver specified in the RD.stanza at some instances?
When you start a CICS application server (cicsas) process, it will wait for the time mentioned in ServerIdleLimit. If the cicsas process does not receive work for ServerIdleLimit seconds, it will verify if there is more than the MinServer cicsas processes running in that region.
If there are more, the cicsas process will get terminated. If cicsas processes running in the region are same as MinServer, then that cicsas process will continue waiting for work.
It is also possible that the number of the cicsas processes might go below the MinServer value for a short duration. This occurs when many processes occur with idle time-outs exactly at the same time and during that time all process finds the current cicsas processes having a count that is more than the MinServer value, and gets terminated.
However, the CICSAM process will restart cicsas process to MinServer immediately.