physical io (on the drive) is aimed to seed the buffer cache where the logical io (database logical) occurs.
How to handle excessive I/O waits?
There are several ways to handle excessive I/O waits. In the order of effectiveness, these are as follows:
- Reduce the I/O activity by SQL tuning
- Reduce the need to do I/O by managing the workload (in the time)
- Gather system statistics with DBMS_STATS package, allowing the query optimizer to accurately cost possible access paths that use full scans
- Add more disks to reduce the number of I/Os for each disk
- Alleviate I/O hot spots by redistributing I/O across existing disks
Documentation / Reference
- Check IO Scripts (Manual querying AWR for trend analysis and capacity planning). Using services even on single instance, give the ablity to get trend information.