COMMIT statement ends a transaction, saving any changes to the data so that they become visible to subsequent transactions. Also, unlocks metadata changed by current transaction. If autocommit is set to 1, an implicit commit is performed after each statement. Otherwise, all transactions which don't end with an explicit
COMMIT are implicitly rollbacked and the changes are lost. The
ROLLBACK statement can be used to do this explicitly.
The required syntax for the
COMMIT statement is as follows:
COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
COMMIT is the more important transaction terminator, as well as the more interesting one. The basic form of the
COMMIT statement is simply the keyword
COMMIT (the keyword
WORK is simply noise and can be omitted without changing the effect).
AND CHAIN clause is a convenience for initiating a new transaction as soon as the old transaction terminates. If
AND CHAIN is specified, then there is effectively nothing between the old and new transactions, although they remain separate. The characteristics of the new transaction will be the same as the characteristics of the old one — that is, the new transaction will have the same access mode, isolation level and diagnostics area size (we'll discuss all of these shortly) as the transaction just terminated.
RELEASE tells the server to disconnect the client immediately after the current transaction.
NO RELEASE and
AND NO CHAIN options. By default, commits do not
CHAIN, but it's possible to change this default behavior with the completion_type server system variable. In this case, the
AND NO CHAIN and
NO RELEASE options override the server default.