Re: Online redo log tuning

The statistic is normal. To delete 50,000 record and add 50,000 record. There is surely certain I/O to perform. Especially Redo Log I/O. You can't reduce, you can just delay. The I/O will occur sooner or later whatever you parameter is. For the I/O on Datafile, it will also occur sooner or later, unless the delete row DB block is same as insert row DB block. You can set a larger Redo Buffer and a larger Redo Log, performance will improve, but I would say less than 10%, or even 3%. In extreme, you can set a extremely large Redo log which can hold all 50000delete and 50000insert, so every I/O may be delayed. BUT you must restart the instance to ensure no log switch during the batch job.

My suggestion is too much work and risk, simply add a hard disk, distribute the I/O.

Michael

Dave Waterworth wrote:

> Hi,
>
> I'm currently tuning a database that is to be used as a emergency backup if
> a main server fails. It's running on a 256Meg server with only one disk.
> I've got a few question re the online redo logs and how there config affects
> tuning.
>
> One session periodically loads a large amount of data into the system
> (deleting 50000 records, then replacing with 50000 new records, over about
> 10 tables). I need to make sure this transaction doesn't peg the system
> (there are only a couple of other sessions active but they may be querying
> the same tables that are being deleted.
>
> I've set up the SGA to be 100Meg with 30Meg Redo Buffer which gives me
> pretty acceptible performance but the disk is still very busy during the
> insert. Using diskmon I see that the online redo logs are the culprits, I do
> not care about recovert at all.
Received on Sat Jul 10 1999 - 13:12:37 CDT