Database Reference
In-Depth Information
In version 12c, pkey format has been changed and pkey consists of two parts: value of 4 billion coloring the pkey
as an undo segment, and 65541 identifying a specific undo segment.
*** 2013-03-17 19:29:41.008
Begin DRM(2) (swin 1) - AFFINITY transfer pkey
4294967295.65541
to 2 oscan 1.1
kjiobjscn 1
ftd (30) received from node 1 (4 0.0/0.0)
all ftds received
Troubleshooting DRM
If your database is suffering from excessive issues due to GRD freeze (and AWR wait events supports that assertion),
then use the following guidelines to debug the problem.
1.
Identify objects involved in DRM activity. Views gv$gcspfmaster_info and gv$policy_history
can be used to identify objects triggered for DRM activity. LMD trace file will show object_id
involved in a DRM with pkey as object_id. Verify if these object_ids are valid object_ids.
In the following example, DRM is triggered on an object
27707121
. Verify this object_id
with dba_objects/cdb_objects(12c) and check if the object is valid. In 12c CDB, you need
to identify the PDB associated with the object.
Rcvd DRM(5) AFFINITY Transfer pkey 27707121.0 to 3 oscan 1.1
2.
Understand if the activity on that object is justified by reviewing application workload
pattern. If the activity is justified, then try to tune the SQL statement accessing those
objects to reduce object access.
3.
Identify the programs/application processes accessing those objects heavily. Colocate
those programs to the same instance.
4.
If none of these actions help, then contact Oracle Support and check if you can reduce
DRM activity by tuning _gc_policy_minimum and _gc_policy_time parameters.
In summary, dynamic remastering is a good feature to improve performance of applications in a RAC database
if the application affinity is in play. You can reduce the RAC tax to a minimal amount with this great feature. Also, in a
RAC one-node database or a RAC cluster with active/passive instances, you can avoid RAC tax completely. It is a pity
that this feature doesn't work for all workloads and especially that this feature starts to be problematic if the SGA size
exceeds 50GB+.
AWR Reports and ADDM
AWR reports
10
and Automatic Database Diagnostic Monitor (ADDM) are the first step in performance diagnosis in a
RAC cluster. There are multiple ways you can generate AWR reports in a RAC environment. You can also use OEM to
generate an AWR report.
To generate an AWR report in a specific instance, use the awrrpti script. You can supply instance and database to
generate AWR reports. In the following example, I am generating AWR report for instance 3.
10
You need a Diagnostics and Tuning pack license to access AWR tables or report.
