Commit is basically use to make your changes permenant. A commit occurs automatically at the end of the program, or by request one or more times during the execution of the program. Releases all locks acquired by the program since the last commit, so that other programs and users may obtain access to the data. Any open cursors are automatically closed. All database changes are made permanent.
thanx priyesh and rupesh as in manual we can lock our table in 2 modes in exclusive and shared mode i have selected exclusive mode,but i am able to do all the operation on that table values r getting inserted and selected then why lock?