for update nowait tips
https://topic.alibabacloud.com/a/differences-between-for-update-and-for-update-nowait-in-oracle_1_46_30119809.html In this example we select a student row and nowait up to 15 seconds for another session to release their lock: select student_last_name from student where student_id = 12345 FOR UPDATE nowait 15; Conversely, in this example we use "for update nowait" and Oracle will immediately fail the transactions if it is waiting on any shared resources (locks or latches): select student_last_name from student where student_id = 12345 FOR UPDATE nowait; SELECT select_clause FROM from_clause WHERE where_clause FOR UPDATE OF column_name; Things to know about row locking in Oracle: SELECT…FOR UPDATE will not be able to lock rows if they are already locked by another transaction. By default, the session will wait for the locks to be released by the other transa...