When auto-commit is disabled (see Using auto-commit), you use a Connection object's commit and rollback methods to commit or roll back a transaction. The commit method makes permanent the changes resulting from the transaction and releases locks. The rollback method undoes all the changes resulting from the transaction and releases locks. A transaction encompasses all the SQL statements executed against a single Connection object since the last commit or rollback.
You do not need to explicitly begin a transaction. You implicitly end one transaction and begin a new one after disabling auto-commit, changing the isolation level, or after calling commit or rollback.
Committing a transaction also closes all ResultSet objects excluding the ResultSet objects associated with cursors with holdability true. The default holdability of the cursors is true and ResultSet objects associated with them need to be closed explicitly. A commit will not close such ResultSet objects. (See Holdable cursors for more information.) It also releases any database locks currently held by the Connection, whether or not these objects were created in different threads.