The Oracle (tm) Users' Co-Operative FAQ
Why is shutdown immediate not immediate ?
| Author's name: Norman Dunbar;
Author's Email: Oracle@bountifulsolutions.co.uk |
Date written: 22/08/2001 Oracle version(s): 8.1.7 |
| Trying to shut the database down, 'shutdown immediate' takes forever - why isn't it immediate ? |
There are four ways to shut down a database :
- Shutdown
- Shutdown immediate
- Shutdown transactional
- Shutdown abort
Shutdown waits for everyone to finish & log out before it shuts down. The database is cleanly shutdown.
Shutdown immediate rolls back all uncommitted transactions before it shuts down. The database is cleanly shutdown.
Shutdown transactional waits for all current transactions to commit or rollback before it shuts down. The database is cleanly shutdown.
Shutdown abort quickly shuts down - the next restart will require instance recovery. The database is technically crashed.
The key reason for an immediate shutdown not being immediate is because of the need to rollback all current transactions. If a user has just started a transaction to update emp set sal = sal * 2 where emp_id = 1000; then this will be rolled back almost instantaneously.
However, if another user has been running a huge update for the last four hours, and has not yet committed, then four hours of updates have to be rolled back and this takes time.
So, if you really want to shutdown right now, then the advised route is :
- shutdown abort
- startup restrict
- shutdown
When you shutdown abort, Oracle kills everything immediately. Startup restrict will allow only dba users to get in but, more importantly, will carry out instance recovery and recover back to a consistent state using the current on-line redo logs. The final shutdown will perform a clean shutdown. Any cold backups taken now will be of a consistent database.
There has been much discussion on this very subject on the Oracle Server newsgroups. Some people are happy to backup the database after a shutdown abort, others are not. I prefer to use the above method prior to taking a cold backup - if I have been unable to shutdown or shutdown immediate that is.
Further reading:
Oracle8i Administrator's Guide - section 3 Starting Up and Shutting Down
