Trace on Standby: Tracing MRP Process

Hey all!
Recently I got the following error when trying to start a trace in a standby. The idea was to start a trace in MRP to check on performance, but when trying to use DBMS_MONITOR.session_trace_enable:

oracle:standby-srvr /tmp: sqlplus / as sysdba

SQL*Plus: Release 12.1.0.2.0 Production on Fri Jan 19 14:07:56 2018

Copyright (c) 1982, 2014, Oracle. All rights reserved.

Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Advanced Analytics and Real Application Testing options

SQL> exec DBMS_MONITOR.session_trace_enable(session_id =>1970, serial_num=>55126, waits=>TRUE, binds=>TRUE);
BEGIN DBMS_MONITOR.session_trace_enable(session_id =>1970, serial_num=>55126, waits=>TRUE, binds=>TRUE); END;

*
ERROR at line 1:
ORA-06550: line 1, column 7:
PLS-00201: identifier 'DBMS_MONITOR.SESSION_TRACE_ENABLE' must be declared
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored

OMG!
Don’t panic, you can accomplish the same using oradebug:

-- In my case:
SQL> select process,pid from V$managed_standby where process like '%MRP%';

PROCESS PID
--------- ------------------------
MRP0 45693

SQL> oradebug setospid 19564
Oracle pid: 105, Unix process pid: 19564, image: oracle@standby-srvr (MRP0)
SQL> oradebug unlimit
Statement processed.
SQL> oradebug Event 10046 trace name context forever, level 12
Statement processed.
SQL>

You can apply same for any process/sid you need.

In case you desire to get the spid from a sid:

col machine format a30
col process format 999999
select p.spid,b.sid, p.pid
from v$session b, v$process p
where b.paddr=p.addr
and sid=&sid
/

Ok, and how to stop then?
Easy:

SQL> oradebug setospid 19564
SQL> oradebug Event 10046 trace name context off
SQL> oradebug tracefile_name

Enjoy!

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