Please define what you consider a hang.
How long did wait for shutdown immediate?
If there are transactions running, it could take awhile.
10-15 minutes is not all that unusual if there are some long running transactions going on.
-- Jared Still Certifiable Oracle DBA and Part Time Perl Evangelist
We have Oracle 18.104.22.168 database ( single Note RAC ). There were some heavy batch jobs running which cuased the db hang ( only sys connection was working ).
We tried to bring down the database after cleaning all sessions. It did not go down with SHUTDOWN IMMEDIATE. We had to abort it. I tried to bring down the DB three times with SHUTDOWN IMMEDIATE it never went down.