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Prior to Ingres II 2.5, when the DBMS fetched a row for a cursor mode update, it would acquire an exclusive lock. In serializable mode, this lock would be held until the end of transaction, even when the row was not updated. In this release, the Ingres DBMS acquires an update mode lock for the row that is a candidate for update. If the row is actually updated, the update mode lock is converted to logical exclusive lock; otherwise, it is converted down to shared lock or released, depending on the current isolation level. Update mode locking is now the default for cursor updates.
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Prior to Ingres II 2.5, the Ingres DBMS would hold a page lock on the leaf pages on B-tree tables for a serializable update transaction, even when using row locking. This was done to prevent other users from inserting a row in the qualified range to be updated. In Ingres II 2.5, the DBMS uses a value locking protocol for serializable transactions with an equal predicate, thereby allowing better concurrency.
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Ingres II 2.5 incorporates a variety of internal enhancements to the compilation and execution of queries.