Firebird 2.1 Language Reference Update

Tip
Transaction control statements
If you expect the volume of changes in your transaction to be large, you can specify the NO AUTO UNDO option
in your SET TRANSACTION statement, or – if you use the API – set the TPB flag isc_tpb_no_auto_undo.
Both prevent the creation of the transaction-level savepoint.
Savepoints and PSQL
Transaction control statements are not allowed in PSQL, as that would break the atomicity of the statement that
calls the procedure. But Firebird does support the raising and handling of exceptions in PSQL, so that actions
performed in stored procedures and triggers can be selectively undone without the entire procedure failing.
Internally, automatic savepoints are used to:
• undo all actions in a BEGIN...END block where an exception occurs;
• undo all actions performed by the SP/trigger (or, in the case of a selectable SP, all actions performed since
the last SUSPEND) when it terminates prematurely due to an uncaught error or exception.
Each PSQL exception handling block is also bounded by automatic system savepoints.
Available in: DSQL, ESQL
Changed in: 2.0
SET TRANSACTION
Description: Starts and optionally configures a transaction.
Syntax:
SET TRANSACTION
[NAME hostvar]
[READ WRITE | READ ONLY]
[ [ISOLATION LEVEL] { SNAPSHOT [TABLE STABILITY]
| READ COMMITTED [[NO] RECORD_VERSION] } ]
[WAIT | NO WAIT]
[LOCK TIMEOUT seconds]
[NO AUTO UNDO]
[IGNORE LIMBO]
[RESERVING | USING ]
::= [, ...]
::= tablename [, tablename ...]
[FOR [SHARED | PROTECTED] {READ | WRITE}]
::= dbhandle [, dbhandle ...]
• The NAME option is only available in ESQL. It must be followed by a previously declared and initialized
host-language variable. Without NAME, SET TRANSACTION applies to the default transaction.
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