Re: DB writer takes over?

Jim Kuschill wrote:

> We've got a database with of about 15GB, spread moderatly over several
> drives, on a mid-size Unix box with 2 CPUs. We've allocated 50,000
> buffers for the hummer, and are not running with archiving. Everything
> runs quite well until we try to do some batch work and post a lot of
> blocks.
>
> Now, we fully expect things to get a little herkey-jerkey, but what
> happens doesn't seem quite right...
>
> The batch update runs along just fine until it apparently runs out of
> blocks. The DB writer fires up ... and locks up the database until it's
> done with its work!
>
> Is this normal? I know there are about a Sagan's-worth of tuning
> paramters, but any clues which might get our DB writer to play nicer?
>
> kusch_at_frequencymarketing.com

Jim,

It's possible that the database is checkpointing (DBWR activity) on one of the log switches, and while it's doing that, the other redo logs get filled and then comes back around on the original redo log. At this point, the database will stop until the checkpoint is done, releasing the redo log.

To verify, you can check v$log, which shows the state of each redo group. If there is one CURRENT and the rest are ACTIVE, then I believe this condition is manifesting itself! Also look for "Checkpoint not complete" messages in the alert log as verification.

To alleviate this, you might try larger and/or more redo logs. Also, more database writers could help finish the checkpoint faster.

Good luck.

Alan.

--
Alan Gano
http://home.att.net/~alangano/index.html Received on Sat Nov 14 1998 - 20:17:36 CST