Monitoring RAC wait events
As the RAC DBA, it is critical to monitor wait events on a regular basis before users complain about performance problems. When you execute AWR and ADDM reports, you should further analyze any wait event that occurs in the top of the AWR report listing.
By taking an holistic approach to monitoring wait events for RAC, you will avoid tunnel vision and discover the root cause of the performance issue. We recommend that you use the ADDM, AWR, and ASH reports as a starting point for RAC performance analysis, as these tools are highly instrumented and provide a bird's eye view into the entire RAC cluster performance. Furthermore, using queries against the V$ views are also very useful in providing thorough information for troubleshooting and performance tuning.
Each RAC instance takes its own AWR snapshot at approximately the same time. Each instance has its own MMON background process writing into AWR repository in the SYSAUX tablespace. The main change in AWR reporting...
