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Redo Log [message #316389]

Thu, 24 April 2008 22:36

enkhbold
Messages: 36
Registered: July 2005
Location: Mongolia

Member

Our database having a problem relating to LGWR.

Monitoring (Spotlight on windows) displays "average time to sync a Redo Log Entry alarm activated when the time taken to write redo log entries during a commit exceeds a threshold".

We thinking it is relating to Redo Log buffer size and writing process.

Redo Lug buffer size is 30MB and Redo files are 200MB each.
Database is Oracle10g RAC 64 bit. And, we allocated dedicated disk to REDO LOG files at the EMC storage.

please advice me on redo sizing and this alarm how to fix?
please share with me experience.

thanks

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Re: Redo Log [message #316456 is a reply to message #316389]

Fri, 25 April 2008 03:15

hristo
Messages: 258
Registered: May 2007

Senior Member

How many logswitches do you have per hour?

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Re: Redo Log [message #317011 is a reply to message #316389]

Tue, 29 April 2008 03:08

halfydba
Messages: 20
Registered: November 2007
Location: Australia

Junior Member

1. "Redo Lug buffer size is 30MB"

Redo log buffer or log_buffer size of 30MB is excessive. This should probably no larger than 1MB as there is no real benefit of having a larger value.
-> Default Maximum is 512 KB or 128 KB * CPU_COUNT, whichever is greater.
Or else you could be causing yourself issue when writing the buffer to your online redo e.g. log file sync issues.

2. "And, we allocated dedicated disk to REDO LOG files at the EMC storage." are you using raid 1? raid 5 is no good for online redo logs when there is reasonable system activity.

Changing these will will probably help your log file sync issues

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Re: Redo Log [message #318147 is a reply to message #317011]

Mon, 05 May 2008 22:37

enkhbold
Messages: 36
Registered: July 2005
Location: Mongolia

Member

Thanks for reply.

1.
I have changed it to 14MB. problem is still same.

And, tried to reduce to 10MB, but doest not changed. I don't know why it is not changed.

2.
RED0_LOG files are locating in dedicated disk (RAID1).

Are there need to apply any patch or update for Oracle and Windows?

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