What is the difference between the below two erros.as far as i understood, they happen in case of a Lock. But do you know the differene in scenarios where one might occure.
ORA-04021: timeout occurred while waiting to lock object
and
ORA-00054: resource busy and acquire with NOWAIT specified
Example for
ORA-04021might be this: there's a package in your schema. It contains a procedure which does some job that takes 15 minutes to finish. Someone runs that procedure. Meanwhile, you'd want to fix something in that package, so you edit its code and want to compile it. Well, you can't - it is being used so you'll have to wait until it is released. Oracle tells you that timeout occurred while you're waiting to lock the package and compile it.Example for
ORA-00054: there's a table. You update some values in it, but didn't commit (nor rollback) as you have to do something else as well. In another session, another user wants to alter one of table's columns (for example, enlarge its size). ALTER will then raise 0RA-00054 which says that table is busy (you're updating it in another session, right?) so you'll have to wait until transaction commits (or rollbacks).