Re: shutdown immediate or abort for cold-backup?

First - these days, I can think of no good reason not to use a hot backup anyway, certainly for production databases, so it's essentially an academic discussion.

However, my point was that either shutdown abort is in itself dangerous or you can safely backup the database after a shutdown abort.

> A shutdown abort is equivalent to a crash, ie a power outage or whatever.
> Do you think you can make a backup of a database which is potentially
> corrupt and will be recovered automatically on the first startup after the
> shutdown abort.

The database is only potentially corrupt if the recovery mechanisms in Oracle are inadequate.

> You can't mean this seriously, can you?
> In the first scenario when the startup restrict succeeds
> you have a working database.

The scenario stated was one in which a database block is incompletely written to disk such that the header scn (or checkdigit?) and the footer scn do not match. If the recovery mechanism is not adequate to recover this error, it is almost certainly not going to report the error i.e. the database will appear to start ok, but there will be a corrupt data block

> In the second scenario you are going potentially to restore a database
which
> is in recovery state.
> Your backup can not be considered to constitute a consistent backup

I repeat - there is no difference between the files on disk at the startup restrict before the backup or after the restore. It does not matter in terms of the consistency of the resulting database wether you do the recovery after the restore or before the backup - either shutdown abort is in itself dangerous or it is not.

shutdown abort
<<< THE FILES ARE THE SAME HERE
startup restrict
shutdown immediate

 shutdown abort
backup the database
restore the database
<<< AS HERE
startup restrict
shutdown immediate

It does matter in terms of the time taken to have a working database again because of the potentially long time before the recovery completes.

> Your assertion there is no difference between the two scenarios is just
> plain nonsense
>

See above. The only difference is that you may find out you have a corrupt database before you back it up - ie shutdown abort has corrupted the database and you have now lost probably a day's work whereas if the database was corrupt and you recover from it you may lose up to two days work (assuming you do a cold backup once per day).

I cannot emphasise enough that in practical terms it should not matter. You should be doing hot backups of production databases. Received on Sat Aug 18 2001 - 08:28:37 CDT