Hi,

There are some papers on metalink about interpratation, but it purely depends on your environment of database.

1. Statspack useful to diagnose the issues for the the period.
2. Regular monitoring (behaviours of I/O subsystems, reads writes on the tablespaces)
3. Monitoring top queries.

If you are on 10g, AWR reports provides more details.

Dilipkumar Patel.