Online redo log tuning

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.

1. I don't need to archive the redo logs, will increasing there size and hence reduce the frequency of log switches have much effect on performance or are log switches fairly cheap?
2. With only 2 1M redo log files, is there a chance that the check pointing of log 1 is still in process when log is full, or is the check point process pretty quick? Does checkpointing block a log switch? Does it matter if a single transaction fills all of the online logs then starts to overwrite the initial file again?
3. The log_checkpoint_interval is set to 10000 which I thinks means that I'm checkpointing far more frequenctly than necessary. How do I disable this, do I delete the entry in init.ora, set it to zero or a larger value?
4. What exactly does the message checkpoint not complete mean and how do I eliminate it
5. I notice that the starter database has two redo log groups, I assume that both are being written too simultaneously which makes no sense on a single CPU single disk machine.

Thanks in advance

Dave Waterworth Received on Tue Jul 06 1999 - 08:19:44 CDT