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Oracle's PMON (process monitor)

The process monitor database process.
This process is in charge to perform process recovery when a user process fails (also when killed). It then cleans up the cache and frees resources that the process used.
PMON checks dispatchers and server processes and restarts them if they have failed.

Service registration

Service registration is a feature which allows an Oracle Server to register itself with a listener. That means that the Oracle Service needs not be configured in the listener.ora configuration file.
During service registration, PMON provides the listener with
  • Names of the database services provided by the database
  • Name of the instance associated with the servie and its current and maximum load
  • Service handlers (dispatchers and dedicated servers)
However, if there is no listener at startup, PMON can obviously not register those information. Therefore, PMON tries then periodically to register with the listener, which might take up to 60 seconds.
It is possible to force this registration with alter system register.

Thanks

Thanks to Kasia Tuszynska who notified my of a typo on this page which is now corrected.