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Re: Redo Log help

From: Svend Jensen <svend.jensen_at_it.dk>
Date: Thu, 29 Aug 2002 20:55:48 +0100
Message-ID: <3D6E7C44.7040301@it.dk>


Rogbaker wrote:

> We are using Oracle 8.1.7 and are in the process of a PeopleSoft
> upgrade test move. We have an APP Engine program running very long and
> and sql script running very long simultaneously. Looking in the alert
> log, I have seen multiple
> 'Cannot allocate new log' and 'Checkpoing not complete' messages.
> These upgrade scripts/programs do move a ton of data. I have added
> more 2 more log groups, which seem to have handled the error messages,
> but how frequently should the database advance to a new log group? It
> is happening like every 30 seconds.
> Right now I have:
> groups #1-5 with 2 10M members
> group #6 with 2 15M members
> group #7 with 2 20M members
>
> Thanks for any help,
> Roger Baker
> Seminole Co. Public Schools
>

Running archive log mode and redo logs on the same device/disk

creates device or io contention on busy systems.

The log writer needs to write redo information end empty the log buffer and the archiver(s) need to read and archive the used log files.

This can be overcome by placing redo logs on several devices that are not busy by themselves. Then log writer is writing its data stream to one device while archiver is reading from one or more of the others.

By having 4 way interleaving on striped disk sets, I had no problem with redo logs and archiving, even if the system filled a 2000M redo log file in ~ 60 seconds. I used 4 * 4 redo logs, 4 logs on each logical unit.

rgds Received on Thu Aug 29 2002 - 14:55:48 CDT

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