DASD Issues

Submitted by admin on Sat, 2004-08-07 07:17.

Spread your data files across discs and channels. Stripe table data with the ALTER TABLE x ALLOCATE EXTENT (DATAFILE y); command.
The I/O rate on rollback segments is extremely high - allocate it on fast devices.
Log files determine COMMIT time performance since all transactions synchronize with it. Allocate log files on fast devices.
Use DASD Fast Write for redo log files. Just make sure nobody will try to flush the disk caches :-)
DFSMS is not supported by Oracle, you can't create storage groups to separate slow and fast devices.
Full table scans can hurt performance. V$SESSTAT can be used to monitor full table scans.
Look-out for DASD hot spots (RMF stats, V$FILESTAT).
20-30 ms response for 3380's vs 8-18 ms for 3390's is typical.