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Process Monitor - PMON
Cleans up cancelled processes
- Performs rollback
- Release locks, latches
- Memory (SGA) cleanup
Monitors other background processes
Registers instance with SQL*Net listener
Notes:
The process monitor background process will clean up after a user process failure. An example of user process failure is when a user cancels a command, perhaps due to lock contention. For example. a user could cancel a process (command) with a CTRL+C from a SQL*Plus session. Note that this does not necessarily mean the session failed. PMON will rollback any uncommitted work, and release any locks, latches and memory. This will be done automatically as the PMON process wakes up periodically.
PMON will also monitor other Oracle processes and, if feasible, restart a failed process. E.g. PMON might restart a failed shared server process. However, if the LGWR process failed, this would be seen as a critical failure, and the instance would crash.
Finally, PMON also registers the instance with the SQL*Net listener running on the server (if available). It would send the listener the instance name so that the listener could route future connection attempts to the instance.