Re: Is an export with consistent=y safe ?

Hi Tommy,

Basically an export protects you against logical error (users accidentally dropping a table or just working)
A backup protects you against physical problems: power outage, headcrash etc.
With an export as the only 'backup' media, you would be forced to rebuild the COMPLETE database.
A database recovery would of course dependent on the size of the data you lost and the size of the archived redo logs take lesser time than recreate the database from scratch.
Please not that a consistent exports issues a series of readonly selects. This means the select data will go into your rollback segments to produce a read consistent view. It is quite probable your rollback segments are not big enough to cope with the amount of data. If that's not the case, the export is consistent yes, but it will never be a replacement for an O/S backup.
I survived (years ago) about one headcrash per month and only thanks to running in archivelog.
When someone accidentally deleted 32 rows from a 3 million records table (I admit: It was me. Mea culpa) and there was NO export, it took us 8 hours to get the data back (restore database, point in time recovery, dump the data, restore database, import 32 rows). You both need backup/archivelog and export. I hope my 'horror' stories have made that clear.

Hth,

Sybrand Bakker, Oracle DBA

Tommy Raun <tr_at_svendts.dk> wrote in message news:37B0281F.E6645B96_at_svendts.dk...
> I am writing a backup script for a Oracle 7 server.
> I'll like to make a online backup in NON-ARCHIVELOG mode.
>
> An export seem to be the only choice. The command for doing that would
> be:
>
> exp consistent=y buffer=300000 file=exp.dmp full=y
>
> However in chapter 23 in Oracle Server Adminstrator's Guide I read the
> following
> sentens:
> "Database exports are not a substitute for operating system backups and
> cannot provide the same complete recovery advantages that the built-in
> functionality of Oracle offers"
>
> Why is the export not 'a substitute for the system backup'? Is
> something important missing in the exportfile or is the data not really
> consistent?
> --
> Regards
>
> Tommy Raun
> tr_at_svendts.dk
Received on Tue Aug 10 1999 - 12:56:59 CDT