You are allowed to run your Oracle database with Oracle Data Guard (physical standby database) by SAP. Oracle itself is publishing “Data Guard Physical Recommended Patch Bundles”, but there is no patch bundle available for 11.2 until now. The following blog will describe one ciritcal issue, that we hit after we have upgraded to Oracle 188.8.131.52 (SBP 112022_201105) and running a physical standby database. We also hit a few other issues and fixed them in our test environment before Go-Live, but these issues depend on your configuration. I will focus on one general critical issue only, that you can’t easily “simulate” in a non productive-environment.
We are running a physical standby database in LGWR SYNC mode without Active Data Guard. The average shipped log volume is round about 3-4 MB per second.
DGMGRL> show configuration;
Configuration – SAP_ERP_P01_DG
Protection Mode: MaxAvailability
p01 – Primary database
s01 – Physical standby database
Fast-Start Failover: DISABLED
After we upgraded our primary database, rebuilt and recovered our standby database – we note a huge CPU load on our standby database server.
The following CPU load graph illustrates a Power 6 CPU based environment in snapshot average of 5 mins. If you are taking some live monitored data the CPU usage is much higher in peak – up to round about 5 to 6 CPUs for round about 2 minutes by running in recovery mode only.
After some researches we found out, that the hight CPU load was caused by the DBWR. If the CPU load increases – you can see “latch free” events for the DBWR processes only.
SQL> select SID, SERIAL#, STATUS, PROCESS, PROGRAM, EVENT from v$session where PROGRAM like ‘%DBW%’;
SID SERIAL# STATUS PROCESS PROGRAM EVENT
———- ———- ——– ———————— ———————————————— —————————————————————-
1 1 ACTIVE 491670 oracle@<hostname> (DBWA) latch free
89 1 ACTIVE 417928 oracle@<hostname> (DBWB) latch free
881 1 ACTIVE 311336 oracle@<hostname> (DBW0) latch free
969 1 ACTIVE 217102 oracle@<hostname> (DBW1) latch free
1057 1 ACTIVE 209030 oracle@<hostname> (DBW2) latch free
1145 1 ACTIVE 471058 oracle@<hostname> (DBW3) latch free
1233 1 ACTIVE 164014 oracle@<hostname> (DBW4) latch free
1321 1 ACTIVE 368716 oracle@<hostname> (DBW5) latch free
1409 1 ACTIVE 532540 oracle@<hostname> (DBW6) latch free
1497 1 ACTIVE 606256 oracle@<hostname> (DBW7) latch free
1585 1 ACTIVE 516224 oracle@<hostname> (DBW8) latch free
As we hit the bug #11866952 – Oracle already know about this issue and provided a patch for Solaris and Linux. Unfortunately we were running on AIX – so we need to request a backport, which was provided within a few hours.
Today Oracle provides this patch for AIX, Linux and Solars on 184.108.40.206 and for Linux on 220.127.116.11. If you are running Oracle on another platform you should request a backport before using Data Guard in your productive environment.
Fortunately this patch is fully compatible with the SBP 112022_201105.