Re: Log file sync and log file parallel write.

From: Hemant K Chitale <>
Date: Thu, 06 Mar 2008 19:55:31 +0800
Message-Id: <>

I won't come back with the blind (sometimes too-quick-off-the-mark) question "why are you rebuilding indexes". There can be valid reasons if you have experience
to show that a rebuild becomes necessary.

What I want to ask is : Are you rebuilding with NOLOGGING ? Gone are the days when Index Rebuild should cause singificant LGWR activity.

10 index rebuilds if *sequential* should be no different than 1 long running query !
There's only 1 process / 1 thread. Are you using Parallelism ? Maybe the server / IO
cannot handle multiple large reads occurring in parallel ? Would certainly be a hardware issue if you have had "timeouts" when reading from disk ! Are you using Async I/O and encountering async timeouts ?

When you say "a simple rebuild of 10 indexes", how large are those indexes ? You could guage the total volume of IO being performed.

Last observation : See if you can switch from REBUILD to DROP and CREATE (or test for a few of these 10 indexes) ? Could be a problem with the particular
blocks the existing indexes are on ?
Hemant K Chitale

At 03:00 AM Tuesday, Johnson, William L (TEIS) wrote:
>A simple exercise of rebuilding about 10 different indexes on-line
>serially takes 45 minutes. s
>Index rebuilds shouldn't be doing this to our system. Our
>production database was crashed yesterday due to other applications
>"timing out" through the cluster while trying to read data while
>this type of activity was occurring.

Hemant K Chitale

"There is more to life than increasing its speed." Mohandas Gandhi Quotes

Received on Thu Mar 06 2008 - 05:55:31 CST

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