Re: AIX: mirrored drives and Oracle corruption

Steve Perry wrote in message <37AF8150.9DF4E927_at_sprynet.com>...
>Hi Norman,
>
>I didn't state it clearly. One of the drives fail, Oracle chokes, AIX
doesn't
>know, shutdown the db, sys admin replaced the drive, we had to recover the
files
>on the mirrored drive. The other half of the mirror was fine. Oracle sensed
the
>problem, but AIX didn't.
>I would have thought AIX would have noticed it and an alert would have been
sent
>to the SA. They would have notified us and scheduled maintenance to replace
it.
>
>Thanks,
>Steve

First of all, if you have a drive "fail" and no errors are reported in the error report, you've got a serious microcode/device driver problem that needs to be addressed. The only time I've ever seen that happen is when the microcode on the drive and adapter are incompatibile, therefore the adapter "doesn't understand" what the disk is telling it and drops the event all together. This is of course a real bad situation.

Second, even if the drive fails and no error is reported, if the LV is properly mirrored AIX should be able to successfully read/write the data to the copy on the mirrored drive. In that scenario, oracle or any other application would never know the error occurred because AIX would be returning a successful I/O completion to the calling application. However; with a microcode incompatibility issue causing "oracle corruption" it is more likely the write to both mirrors are failing to complete successfully.

There is one other possibility here. At AIX 4.3.2 on the 7017/S7x systems a problem has been noted such that oracle LV's become corrupted. If your system meets this criteria, then you need the workaround APAR.

Otherwise, check your mirroring by running "lslv -m {lvname}" and ensuring that no LPs map to two PPs on the same disk. This would be a problem which would cause you to lose data in a mirrored environment and in fact if the LV's are laid out that way I would tend to ask why mirror at all as it servers no usefull purpose. A simple "lslv {lvname}" should show you COPIES: 2, and the number in the PPs: entry should be twice the number in the "LPs:" attribute. If not, mirroring is not even turned on.

Good luck. Received on Tue Aug 10 1999 - 00:55:33 CDT