A Bit of Theory

The architecture of a basic engine has become very complex, as shown in the following diagram (note that this is only a simplified overview of the Oracle architecture).

The complexity is such that user expertise in one version of Oracle is partly outdated as soon as the next version is released:

Figure 9.2: A simplified description of Oracle architecture

Each part of this architecture can be tuned based on the expected usage of the database.

Add to this the fact that misconfigured databases or unoptimized SQL queries are the cause of most common performance problems, and you can understand the importance of performing load tests on the database server.

For those who are not yet convinced of the importance of tuning the database engine architecture, the following graph shows an example of the response time of a SQL query on Oracle without tuning (where SGA, one of the Oracle database caches, is not correctly configured) versus an optimized Oracle (where the size...