Higher CPU Utilisation on failover node under same workload
- From: "Osborne, Chris" <Chris.Osborne@xxxxxxxxx>
- To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 5 Nov 2014 13:20:10 +0000
Hi all,
This is my first post.
I have an ongoing issue where I am seeing much increased CPU utilisation when a
database is running on the failover node, compared to when it is running on the
primary node.
When we perform OS patching we fail from one node to the DR site, while the
primary site is being patched.
Both hosts are the same spec and config, and the database is configured
identically on both hosts too.
AWR Diff reports show that the workload is very similar.
The 2nd period is where we see the problem
1st
2nd
------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------
Event Wait Class Waits Time(s) Avg
Time(ms) %DB time Event Wait Class
Waits Time(s) Avg Time(ms) %DB time
------------------------------ ------------- ------------ ------------
------------- ----------- ------------------------------ -------------
------------ ------------ ------------- -----------
db file sequential read User I/O 4,178,196 23,392.4
5.6 61.7 CPU time N/A
38,985.7 N/A 59.8
CPU time N/A 10,138.9
N/A 26.8 db file sequential read User I/O 4,581,489
23,083.5 5.0 35.4
read by other session User I/O 325,114 1,866.3
5.7 4.9 db file parallel read User I/O 219,007
1,670.0 7.6 2.6
db file parallel read User I/O 177,766 1,419.6
8.0 3.7 read by other session User I/O 246,088
1,307.7 5.3 2.0
enq: TX - row lock contention Application 1,220 1,321.2
1083.0 3.5 enq: TX - row lock contention Application 651
618.6 950.2 0.9
--------------------------------------------------------------------------------------------------------------------
Host Configuration Comparison
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1st 2nd
Diff %Diff
----------------------------------- -------------------- --------------------
-------------------- ---------
Number of CPUs: 256 256
0 0.0
Number of CPU Cores: 32 32
0 0.0
Number of CPU Sockets: 4 4
0 0.0
Physical Memory: 261632M 261632M
0M 0.0
Load at Start Snapshot: 32.61 57.98
25.37 77.8
Load at End Snapshot: 33.13 63.91
30.78 92.9
%User Time: 6.03 4.95
-1.07 -17.9
%System Time: 4.82 15.19
10.37 215.1
%Idle Time: 89.15 79.86
-9.29 -10.4
%IO Wait Time: 0 0
0 0.0
Cache Sizes
I know that we have a problem with the size of the connection pools on this
database, and the fact that they are dynamic too concerns me. This issue is
being worked on.
My first thought is that fact that the single block read time is 10% faster
could be meaning more of the sessions are runnable at any given point and
slowing us down through context switching, but this may be a stretch...
I am seeing the host reporting more CPU time spent on SYS rather than User time
though.
Any advice/pointers would be gratefully received.
Cheers
Chris
Christopher Osborne
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