Most global cache wait events that show a high total time as reported in the AWR and Statspack reports or in the dynamic performance views are normal and may present themselves as the top database time consumers without actually indicating a problem. This section describes frequent wait events that you should be aware of when interpreting performance data.
If user response times increase and a high proportion of time waited is for global cache, then you should determine the cause. Most reports include a breakdown of events sorted by percentage of the total time.
It is useful to start with an ADDM report, which analyzes the routinely collected performance statistics with respect to their impact, and points to the objects and SQL contributing most to the time waited, and then moves on to the more detailed reports produced by AWR and Statspack.
Wait events for Oracle RAC include the following categories: