Originally posted by sreddy
First thing I would do is check for any third party monitoring tools agents jobs or back ground jobs which will be continuously running and never let your datbase to come down in normal/immediate modes.
Setting NORMAL option asside for obvious reasons, no third party agent or back ground job that is "continuously" running on the database should have a particular influence on the speed/ability to perform SHUTDOWN IMMEDIATE.

Of course there is allways the possibility for us to hit some bug while performing shutdown immediate that could prolong the actual shutdown time to something very close to infinity - there were many bugs related tu shutdown immediate with various releases in the past....