Bad application performance on Oracle RAC

If you are using Oracle 10g, then you can use Grid Control to locate your performance bottlenecks. Point your browser to your Grid Control and click on the Performance tab. The charts will show you were your performance is at its worst. If you have configured your browser with the SVG plug-in (there is a link on the Performance page to download this plug-in), you can even drill down in your worst trouble areas.

Otherwise, the first thing to check is to ensure that your cluster interconnect is configured correctly and that there is no other traffic on this interconnect. The interconnect should be a private network that only lets one node see any other node in the cluster. The interconnect should not be used for anything else as this can cause performance problems.

If the interconnect is configured correctly, and you still cannot determine where your bottlenecks lie, you can query GV$SYSTEM_EVENT to see the top wait events causing your performance problems. For the most part, working with wait events in RAC is just like working with wait events in a single-node environment.