Explain plan

Explain plan will tell us whether the query properly using indexes or not.whatis the cost of the table whether it is doing full table scan or not, based on these statistics we can tune the query.

The explain plan process stores data in the PLAN_TABLE. This table can be located in the current schema or a shared schema and is created using in SQL*Plus as follows:

SQL> CONN sys/password AS SYSDBA

Connected

SQL> @$ORACLE_HOME/rdbms/admin/utlxplan.sql

SQL> GRANT ALL ON sys.plan_table TO public;

SQL> CREATE PUBLIC SYNONYM plan_table FOR sys.plan_table;