Changes to Table-Level Locking

Performing an update or delete via a table scan does not acquire a table-level exclusive lock as it did in earlier versions. In version 11.9.2, the scan acquires an exclusive intent table lock when the transaction starts. When the scan locates a row that must be updated, it acquires an exclusive page or row lock, depending on the locking scheme. The only exception is an unindexed update or delete to a data-only-locked table at transaction isolation level 3; these updates acquire an exclusive table lock. In previous versions, any update or delete that does not use an index acquires a table-level exclusive lock at the start of the transaction.

In most cases, performing the scan without using a table level lock increases concurrency. However, some applications may experience one of these problems: