Destroys a savepoint previously defined in the current transaction.
Destroying a savepoint makes it unavailable as a rollback point, but it
has no other user visible behavior. It does not undo the effects of commands
executed after the savepoint was established. Destroying a savepoint when it is no
longer needed allows the system to reclaim some resources earlier than transaction end.
ReleaseSavepoint also destroys all savepoints that were established after the named savepoint was established.
If multiple savepoints have the same name, only the one that was most recently defined is released.