Oracle Database - Trace File 10053 to understand the Optimizer (CBO)

The reason for examining a 10053 is typically to understand why the CBO made its decisions. The 10053 will help answer the question:

• “Why was my index not used?” or the related,
• “Why did the CBO choose an FTS?”.

The 10053 is typically not the best place to start looking for tuning opportunities:

• the execution plan
• and TKProf

have better information in this regard.

The 10053 is used for deeper cause determination.

• CASE STUDY: Analyzing 10053 Trace Files