The
Process Monitor Process (PMON) periodically checks all
processes to find any that have died abnormally. If it finds such a process, PMON initiates and coordinates the
Cleanup Main Process (CLMN) and the
Cleanup Slave Process slaves (CLnn).
PMON runs as an operating system process, and not as a thread. In addition to database instances, PMON also runs on
ASM instances and Oracle ASM Proxy instances.