The API functions isc_start_transaction() and isc_start_multiple() will now reject combinations of transaction parameter buffer (TPB) items that do not “belong together”.

For example, a non-zero wait timeout is inconsistent with the no wait option; and no record version is inconsistent with any transaction isolation mode other than ReadCommitted. Now, instead of making some arbitrary (and possibly incorrect) assumption about the inherent ambiguities, the engine will reject such combinations as invalid.

For more information, see the topic Transaction Diagnostics in the chapter Changes in the Firebird Engine.

New SQL_NULL constant was introduced to enable the predication OR ? IS NULL to be recognised and processed with the expected outcome and without engendering the “Data type unknown” exception. This affects how the XSQLVAR structures are populated for such queries. For information, refer to the topic SOME_COL = ? OR ? IS NULL Predication in the DML chapter.