Quote Originally Posted by reydp
doing checkpoint manually through "alter system" and issuing a shutdown abort after is basically the same of issuing a command of shutdown immediate.
So there is no need for crash/instance recovery to perform because all datafiles have been in sync, not unless there were pending/ongoing process executed during those commands that will generate new redo blocks.
I disagree. Oracle will have to perform crash recovery as the database was not closed in a consistent state. The checkpoint means that only a fairly small amount of redo will have to be applied, but it still has to be recovered. Oracle background activities can generate redo, so redo is generated even if there is no users in the database.