Listener Registration Process (LREG)
The listener registration process (LREG) registers information about the database instance and dispatcher processes with the Oracle Net Listener (see "The Oracle Net Listener"). When an instance starts, LREG polls the listener to determine whether it is running. If the listener is running, then LREG passes it relevant parameters. If it is not running, then LREG periodically attempts to contact it.
Note:
In releases before Oracle Database 12c, PMON performed the listener registration.
