Shutdown of RAC DB instance is taking very long time showing error: kponepms: encountered ORA-12535

 Problem:

While trying to shut down a 19c RAC DB instance using srvctl command with IMMEDIATE shutdown option, the instance shutdown was taking a significantly long time, at the same time the DB alertlog was showing this error frequently:

kponepms: encountered ORA-12535 for location net8://(ADDRESS=(PROTOCOL=tcp)(HOST=10.1.1.105)(PORT=10809))?PR=0 subname "SYS"."ALERT_QUE":"HAE_SUB" after 7200000 milisecs 

Using ABORT option in srvctl command, still developing same symptoms:

# srvctl stop instance -d dbx -i dbx1 -o abort -force

I decided not to act as per the book anymore, and end up this embarrassment by issuing "SHUTDOWN ABORT" command from a new SYSDBA SQLPlus session!

Analysis:

I used to disable AQ & Jobs 15 minutes before Shutting down the DB to avoid the time jobs will consume for rolling back transactions.

Solution:

Make sure to set AQ and Jobs parameters to at least =1, rather than setting them to 0 before the shutdown of the DB:

SQL> alter system set aq_tm_processes=1;
SQL> alter system set job_queue_processes=1;

If you still face the same issue, then you may need to set the following hidden parameter (you have to consult Oracle Support before setting it):

SQL> alter system set "_client_enable_auto_unregister"=true scope=BOTH sid='*';