CPU Time Wait Event

Question

I am running perfstat in Oracle9i Enterprise Edition Release 9.2.0.4.0. When I create a perfstat report using the standard scripts I see a wait event called "CPU time." I don't understand what this means. The OEM server monitoring tool does not indicate that the CPU is being used more than 50%, often more like 20%. The top 5 wait events is below.
What does "CPU time" time mean?
the following top 5 wait events:
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
CPU time 2,200 61.88
db file sequential read 113,042 639 17.96
control file parallel write 9,345 471 13.24
log file sync 4,722 122 3.44
db file scattered read 13,375 67 1.87

Answer 1

Hi,
Below is part of my Statspack
```````
Snap Id Snap Time Sessions Curs/Sess Comment
Begin Snap: 13805 26-Mar-08 08:00:03 85 173.2
End Snap: 13806 26-Mar-08 09:00:05 98 154.4
Elapsed: 60.03 (mins)
Cache Sizes (end)
~~~~~~~~~~~~~~~~~
Buffer Cache: 1,024M Std Block Size: 8K
Shared Pool Size: 400M Log Buffer: 2,048K
Load Profile
~~~~~~~~~~~~ Per Second Per Transaction
Redo size: 183,878.75 16,898.36
Logical reads: 61,602.61 5,661.25
Block changes: 1,255.54 115.38
Physical reads: 7,370.56 677.35
Physical writes: 55.64 5.11
User calls: 341.11 31.35
Parses: 56.26 5.17
Hard parses: 0.32 0.03
Sorts: 56.43 5.19
Logons: 0.80 0.07
Executes: 712.67 65.49
Transactions: 10.88
% Blocks changed per Read: 2.04 Recursive Call %: 82.56
Rollback per transaction %: 9.29 Rows per Sort: 1043.63
Instance Efficiency Percentages (Target 100%)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Buffer Nowait %: 99.98 Redo NoWait %: 100.00
Buffer Hit %: 88.06 In-memory Sort %: 100.00
Library Hit %: 99.96 Soft Parse %: 99.42
Execute to Parse %: 92.11 Latch Hit %: 99.95
Parse CPU to Parse Elapsd %: 69.60 % Non-Parse CPU: 99.64
Shared Pool Statistics Begin End
Memory Usage %: 89.25 89.26
% SQL with executions>1: 40.51 39.68
% Memory for SQL w/exec>1: 29.05 29.45
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
CPU time 9,272 43.73
db file sequential read 5,203,772 7,027 33.14
db file scattered read 2,198,721 1,547 7.30
log file parallel write 20,935 1,126 5.31
log file sync 10,277 759 3.58
``````````````````
From my observation I found that it seems CPU is bottneck on this Server. I have gathered few SQLs to find out whether any scope for tuning but still I believe that by reducing the cache size also I can divide the load or can say transfer the load from CPU to I/O. Am I correct or do I need to look over else ?
Thanks
MJ