In a COMMIT, all the changes made by a transaction or a subtransaction are recorded in the database instance. The locks assigned to the transaction are released, and a new transaction is opened implicitly.
Changes closed with a COMMIT can no longer be reversed with a ROLLBACK.
In normal database operation, the database system performs the required COMMIT actions without user interaction. However, a COMMIT can also be explicitly requested using appropriate SQL statements (see Reference Manual under COMMIT Statement).