This afternoon I implemented a change to add a column to a table, then Wintel team did some tasks and asked application team to verify the update.
After some minutes we got a S2 ticket from the user side!
I believed the ticket should be not related with the DB change, as I just added a column.
Right? Right?
I mentioned this change with Gary, and he told me if I added a column, then some objects would become invalid, maybe -- just maybe -- the application would run abnormally. I know the invalid objects will be compiled when they are executed, but if some objects are dependent indirectly, what will happen? The ticket should not be a DB issue, as we did not get any Ora error from the application side, while I thought I should compile the invalid objects ASAP, and I did.
After that, I got below webpages about the object dependence:
Schema Object Dependencies(Oracle11.1)
Enhanced Finer Grained Dependency Management in Oracle Database 11g Release 1
Managing Object Dependencies(Oracle11.2)
I feel my database knowledge should be updated soon. 
