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:

have better information in this regard.

The 10053 is used for deeper cause determination.

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