usage of trace 10053..

Use the following command to trace on a sql statement a user is executing
Alter session set event s'10053 trace name context forever 1' ;

To stop trace use the command
Alter session set event s'10053 trace name context off;
The trace gets generated in user_dump_destinatino...


Now the parts of the trace file
Query
Parameter used by optimizer
Base Statistical Info
Base Table Acces Cost
General Plan
Reosting for sepcial featur

There are very nice articles written on tuning in the following
website
www.hotsos.com