Re: DRWR

From: Stefan Koehler <contact@xxxxxxxx>
To: oracle455@xxxxxxxxx, moizarshad@xxxxxxxxx
Date: Fri, 9 Oct 2015 09:50:07 +0200 (CEST)

Hi guys,
just in addition to Moiz reply and as Michael is also using ZFS.

Oracle asked us to get this percentage lower, so system admin added disks, as
soon as the percentage was lower than 80%, log file sync issue
resolved.

This is caused by ZFS fragmentation and the used copy-on-write approach. The
whole behavior is also described in this paper in more detail - sorry
that it is in german, but you can still interpret the graphs:
https://www.yumpu.com/de/document/view/15431428/was-sie-von-oracle-uber-zfs-nicht-horen-werden-de-trivadis

We also discussed the ZFS stuff on OTN some time ago:
https://community.oracle.com/thread/2604168

Best Regards
Stefan Koehler

Freelance Oracle performance consultant and researcher
Homepage: http://www.soocs.de
Twitter: @OracleSK

Moizuddin Arshad Mohamed <moizarshad@xxxxxxxxx> hat am 8. Oktober 2015 um
23:00 geschrieben:

Hi Michael,

I have been in to the similar issue sometime back. Seems to be almost same
issue. What file system are you using?

We increased the SGA, DBWR and also redo logs were moved to a different
disk, faster.
We were using Veritas ZFS file systems. After trying all these, still log
file sync issue continues......

Later Oracle export from ZFS was involved, they applied some kernel level
patches (not sure as I am not a sys admin) but prominently, the ZFS file
system disk of pools was above 90% usage.... Oracle asked us to get this
percentage lower, so system admin added disks, as soon as the percentage
was lower than 80%, log file sync issue resolved.

Hope this would help.

Thanks,
Moiz

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References:
- DRWR
  - From: Michael Calisi
- Re: DRWR
  - From: Moizuddin Arshad Mohamed

Re: DRWR

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