After Patch: MRP0: Background Media Recovery terminated with error 10485

Ok,
I had that some time ago after applying Patch 27475598 – Oracle JavaVM Component 11.2.0.4.180417 Database PSU.
Why? Well, this is Non RAC-Rolling Installable and also Not Data Guard Standby First Installable.

This means there downtime for this patch, no escape.

I had to (skipping all the standard opatch steps, you can see those on README):

• Stop DG Replication:

dgmgrl /
show configuration
show database mydg
edit database 'mydg' set state='apply-off';
show database mydg

• Run postinstall.sql in upgrade mode with only 1 instance on (disable RAC):

cd $ORACLE_HOME/sqlpatch/27475598
sqlplus /nolog
SQL> CONNECT / AS SYSDBA
SQL> STARTUP
SQL> alter system set cluster_database=false scope=spfile;
SQL> SHUTDOWN
SQL> STARTUP UPGRADE
SQL> @postinstall.sql
SQL> alter system set cluster_database=true scope=spfile;
SQL> SHUTDOWN
SQL> STARTUP

Ok, all good, seems all fine.

But now when starting my DG replication:

dgmgrl /
show configuration
show database mydg
edit database 'mydg' set state='apply-on';
show database mydg

What I see is:

DGMGRL> show database mydg

Database - mydg

  Role:            PHYSICAL STANDBY
  Intended State:  APPLY-ON
  Transport Lag:   0 seconds (computed 1 second ago)
  Apply Lag:       41 minutes 53 seconds (computed 1 second ago)
  Apply Rate:      (unknown)
  Real Time Query: OFF
  Instance(s):
    myprod

  Database Error(s):
    ORA-16766: Redo Apply is stopped

Database Status:
ERROR

DGMGRL>

And on Database Alert Log:

MRP0: Background Media Recovery terminated with error 10485
Errors in file /u01/app/oracle/diag/rdbms/axwest/greporaprod/trace/greporaprod_pr00_42628.trc:
ORA-10485: Real-Time Query cannot be enabled while applying migration redo.
Completed: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION
Recovery interrupted!
MRP0: Background Media Recovery process shutdown (greporaprod)

Well, in my case it happens because I use an Active Dataguard, in open read only. The solution? Start you DG in Mount Mode to apply the patching replication!

This is well described as per MOS: MRP process getting terminated with error ORA-10485 (Doc ID 1618485.1).

After getting sync, you can simple promote it to read only mode again.

Hope it helps!