2002-07-26 START TRANSACTION SQL - Language Statements START TRANSACTION start a transaction block START TRANSACTION [ ISOLATION LEVEL { READ COMMITTED | SERIALIZABLE } ] 1998-09-27 None. 1998-09-27 START TRANSACTION Message returned if successful. WARNING: BEGIN: already a transaction in progress If there is already a transaction in progress when the command is issued. This command begins a new transaction. If the isolation level is specified, the new transaction has that isolation level. In all other respects, the behavior of this command is identical to the BEGIN command. The isolation level of a transaction can also be set with the command. If no isolation level is specified, the level defaults to READ COMMITTED. SERIALIZABLE is the default level in SQL. PostgreSQL does not provide the isolation levels READ UNCOMMITTED and REPEATABLE READ. Because of multiversion concurrency control, the SERIALIZABLE level is not truly serializable. See the User's Guide for details. In SQL99 this statement can specify two other properties of the new transaction: whether the transaction is read-only and the size of the diagnostics area. Neither of these concepts are currently supported in PostgreSQL.