LREG Background Process

 LREG (Listener registration Process):dynamic listener registration

This is introduced from oracle 12c onwards, previously the same job is done by the PMON process of the oracle database 

Prior to oracle 12c , PMON used to register the database information  to the Listener process , infact it used to do service_update, service_register, service_died. 

In order to reduce the load on PMON LREG process will do the following actions 

-> Registers instance information with the listener

-> if the LREG process got killed then automatically instance will go down

-> It does service_update, service_register, service_died.

command to trace dynamic registration 

alter system set events='immediate trace name listener_registration level 0';