Cost-Based Oracle Fundamentals

CHAPTER 14The 10053 Trace File

It would be impossible to write a good book on the cost based optimizer without mentioning the optimizer debug trace event: 10053. It is well known that the 10053 trace file can tell you a lot about what the optimizer is doing to calculate the cardinalities and costs involved in evaluating an execution plan. The information is never complete, and there are all sorts of oddities that might exist in such a trace file. But, for your entertainment, this chapter walks through the 10053 trace from a simple four-table join run under 10gR1, describing some of the features that it exposes.

To enable the 10053 trace, you need to issue one of these statements:

alter session set events '10053 trace name context forever';