Re: shutdown abort

Jeff Hunter wrote:
>
> A shutdown abort is a last resort to get your database down. Uncommitted
> transactions are not resolved. When the database comes back up, usually
> there is some recovery that needs to be performed either manually or Oracle
> handles it automatically. This method is not recommeded by Oracle and I can
> agree. However, in theory, if you shutdown abort and backup all the
> database files, recovery would still take place when the database was
> brought back up. This is one of those facts that you would like to know,
> but shoudn't rely on.

A common misconception holds that shutdown abort is somehow more dangerous or reckless than the other shutdown modes, and can result in data being lost. This is not the case. Shutdown abort terminates the Oracle background and shadow processes, and removes the shared memory segments, effectively terminating a running instance. This leaves all committed transactions intact in the online redologs, even if the data associated with them has not been written to the datafiles. Upon startup, recovery is applied from the online logs beginning from the time of the most recent checkpoint. When recovery is complete, the database is opened for use. Transaction rollback occurs in the background after startup, so no user's time is wasted waiting for all uncommitted transactions to roll back.

When starting up after a shutdown abort, the amount of time spent in instance recovery depends largely upon how recently the last checkpoint was issued. By forcing a checkpoint immediately prior to issuing shutdown abort, the redo required to complete crash recovery and bring the database open will be minimal.

The alternative in an active environment to shutdown abort is shutdown immediate, but immediate shutdowns take too long, rolling back transactions and performing other tasks while precious seconds pass by.

Shutdown abort can come in handy for very brief downtimes, such as those required to change a non-dynamic initialization parameter. In practice on Oracle instances with very large SGAs, such quick "bounces" can typically take as little as 25 seconds. --
Jeremiah Received on Thu Dec 02 1999 - 15:40:41 CST