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Odd Database issue with sudden I/O wait
This DB is the backend to Oracles AS/Portal, its the MDR/Infrastructure.
The tuning has always been about CPU reduction, always been CPU bound. Twice Oracle recommended using less memory and I/O wait has never been the issue it usually is inside a Datawarehouse. We successfully load tested 2200 simulated concurrent users on the stack. We were all ready to head home when friday and launch sunday night when the application engineers were re-deploying their application and the Database went to 99% I/O Wait. Nothing could be identified as the cause. Eventually we restored our backups from the night before and to our astonishment the high I/O wait resumed immediately.
I got a Sev 1 Tar opened up and worked it through the nite with support in India. They never turned anything up with the DB. Hours later it dropped from 99% I/O Wait to much lower but still higher than at any time in the past, much too high for an idle DB connected to 2 AS servers.
I still think this is an I/O subsystem degradation due to a broken mirror or something, semi-failed controller. Hardware guys dismiss it immediately.
Any ideas ? Statspack, Enterprise manager have been utilized / uploaded / pondered but to no avail.
I say hardware.
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