15.1 Introduction

In the previous chapter, the discussion was centered around tuning a single instance configuration of the Oracle database. We stated that a methodology should be created/defined and followed during performance testing of the application and the database. We discussed how the application could be divided into quadrants and performance testing each quadrant through an iterative cycle. There are two ways of approaching the performance tuning of the application. One way is a top-down approach where the application tier is performance tuned first, then the instance, and subsequently the database. Another way is a bottom-up approach where the storage system is tuned first, followed by the database, instance, and application. While the second approach has less impact on the application, using the top-down approach is more robust.

We discussed the tuning aspects of the application tier, followed by the Oracle instance, and then looked at the areas to tune in a database tier by discussing the various I/O-related wait events. There were also discussions regarding areas of the system that are influenced by certain waits and what remedies could be applied to reduce their impact.

Clustered instance and database tuning should commence only after the single instance tuning has completed. There is an old quote, 'A stitch in time saves nine.' If you do not complete the single instance tuning before tuning the cluster, it will be a terrible mistake, and if this approach is taken, you will need to include additional days/weeks in the implementa tion project plan...