The Firebird 5.0 Language Reference | Transaction Statements | SET TRANSACTION | Transaction Parameters

`NO AUTO UNDO`

The NO AUTO UNDO option affects the handling of record versions (garbage) produced by the transaction in the event of rollback.With NO AUTO UNDO flagged, the ROLLBACK statement marks the transaction as rolled back without deleting the record versions created in the transaction.They are left to be mopped up later by garbage collection.

NO AUTO UNDO might be useful when a lot of separate statements are executed that change data in conditions where the transaction is likely to be committed successfully most of the time.

The NO AUTO UNDO option is ignored for transactions where no changes are made.

`RESTART REQUESTS`

According to the Firebird sources, this will

Restart all requests in the current attachment to utilize the passed transaction.

— src/jrd/tra.cpp

The exact semantics and effects of this clause are not clear, and we recommend you do not use this clause.

`AUTO COMMIT`

Specifying AUTO COMMIT enables auto-commit mode for the transaction.In auto-commit mode, Firebird will internally execute the equivalent of COMMIT RETAIN after each statement execution.

Caution

This is not a generally useful auto-commit mode;the same transaction context is retained until the transaction is ended through a commit or rollback.In other words, when you use SNAPSHOT or SNAPSHOT TABLE STABILITY, this auto-commit will not change record visibility (effects of transactions that were committed after this transaction was started will not be visible).

For READ COMMITTED, the same warnings apply as for commit retaining: prolonged use of a single transaction in auto-commit mode can inhibit garbage collection and degrade performance.

`IGNORE LIMBO`

This flag is used to signal that records created by limbo transactions are to be ignored.Transactions are left “in limbo” if the second stage of a two-phase commit fails.

Note	Historical Note `IGNORE LIMBO` surfaces the TPB parameter `isc_tpb_ignore_limbo`, available in the API since InterBase times and is mainly used by gfix.