Tuning Global Cache - Expert Oracle RAC Performance Diagnostics and Tuning - page 414

Manual Remastering
As discussed earlier, mastering and remastering of objects based on usage is a default behavior starting with Oracle
Database 11g Release 2. However, in situations when we need to decide the location of the master irrespective of the
usage to control performance, it can be done manually.

Workshop—Manual Remastering of Objects
Manual remastering of objects is done using the ORADEBUG utility that is not documented by Oracle. Use of this feature
should be done in a test environment only to understand and test the GCS behavior. However, if such a change is
required in the production environment, prior consent from the Oracle Support team is suggested.

Step 1
Determine the current masters of the various objects using the GV$GCSPFMASTER_INFO view. From the output
following, XW_INV_DAYBAL_F_U1 is an object of type index partition and is currently managed on instance 8. It is
probably stuck on that instance while all the access related to that object is currently on instance 1. The reason the
remaster operation is taking a longer time than expected is due to several things such as intensive CPU usage, lack of
memory, paging, and swapping. The GCS processes are really busy and not able to keep up with requests.

INT OBJID ONAME OT GC_MP CM PM CNT
---- --------- --------------------- ---- ----------- --- --- ----
1 492984 XW_INV_DAYBAL_F_U1 IP Affinity 8 6 6

Step 2
Using the ORADEBUG utility, several of Oracle diagnostic operations can be performed either using the built in functions
such as LKDEBUG (for RAC-related troubleshooting) or using trace commands to dump data for various components of
the Oracle environment into trace files.
In the output following, partitioned index object with object id 492984 is being remastered to the local instance
where the command is now being executed.

■ Note object id used for remastering objects is the DATA_OBJECT_ID from DBA_OBJECTS.

SQL> oradebug lkdebug -m pkey 492984
Statement processed.

Step 3
The object is now remastered to instance 1, and the status of the object can be verified using the same query used
in Step 1:

INT OBJID ONAME OT GC_MP CM PM CNT
---- --------- ----------------------- ---- ----------- --- --- ----
1 492984 XW_INV_DAYBAL_F_U1 IP Affinity 1 8 7