A named query that sets an exclusive pessimistic on the entities returned by the query by setting the NamedQuery lockMode element to LockModeType.PESSIMISTIC_FORCE_INCREMENT. The application starts…

Question

Options

• AOnly the current transition may modify or delete the entity instances.
• BThe current transaction may NOT modify or delete the entity instances.
• COther concurrent transactions may modify or delete the entity instances.
• DOther concurrent transactions may modify but MAY NOT delete the entity instances.

• A
  79% (31)
• B
  13% (5)
• C
  3% (1)
• D
  5% (2)

Explanation

The lock modes LockModeType.PESSIMISTIC_READ, LockModeType.PESSIMISTIC_WRITE, and LockModeType.PESSIMISTIC_FORCE_INCREMENT are used to immediately obtain long- term database locks. The semantics of requesting locks of type LockModeType.PESSIMISTIC_READ, LockModeType.PESSIMISTIC_WRITE, and LockModeType.PESSIMISTIC_FORCE_INCREMENT are the following. If transaction T1 calls for a lock of type LockModeType.PESSIMISTIC_READ or LockModeType.PESSIMISTIC_WRITE on an object, the entity manager must ensure that neither of the following phenomena can occur: P1 (Dirty read): Transaction T1 modifies a row. Another transaction T2 then reads that row and obtains the modified value, before T1 has committed or rolled back. P2 (Non-repeatable read): Transaction T1 reads a row. Another transaction T2 then modifies or deletes that row, before T1 has committed or rolled back. PESSIMISTIC_FORCE_INCREMENT Pessimistic write lock, with version update.

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