OS - AIX 3
Oracle - 9.2.0.8
We recently switched over from async IO to CIO. [filesystemio_options
to setall]
Reason for this move was a lot of log buffer and log sync waits.
Contrary to the expectation, we have noticed performance degradation
in our batch jobs.
System Event Total Waits Timeouts Time Waited
db file sequential read 234,932,597 0 516,917
db file scattered read 104,119,285 0 218,360
rdbms ipc message 38,010,738 1,642,294 5,860,312
PX Deq: Execution Msg 31,088,553 105,763 237,518
PX Deq: Execute Reply 24,608,715 2,489 84,274
direct path read 22,753,359 0 92,395
PX Deq: Table Q Normal 19,672,286 16,399 66,533
buffer busy waits 19,514,194 5,524 55,345
Though log buffer and log sync waits have disappeared, but sequential
read and scattered read waits have increased.
One recommendation that came forward was to increase db cache size.
Reason behind this was as there is no OS level caching with CIO and
oracle needs to manage it, we need a large db cache size.
I just wanted to know if anyone has run into a similar situation and
if increasing db cache size is the right direction.
Sincerely,
Atul
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