Recovery info on aaaaaaaa.cnf

>   I find references now and again to aaaaaaaa.cnf (principally in Mike
> Leo's Ingres World 95 paper "Safe & Recoverable CA-Openingres Database
> Backup").  He says to back up that file as a separate item (because the
> a*.cnf on the backup tape isn't valid for the tape [for what then?].
> 
>   The DBA Guide, Ch 16, makes no mention of that file.  So then, do you
> really need a separate backup of a*.cnf (and are the Ingres manuals
> overlooking something)?
> 
>   So far, in about 6 or 7 years, we haven't had a catastrophic crash.
> We've had a table or two accidentally dropped, and have been able to
> restore them.  (We're at OI 1.1/04 (hp8.us5/00).)  But Catastrophic
> Crashes always happen, it's just a matter of when.
> 
> 
> thanks,
> 
> Mike Zorn
> Boeing North American, Anaheim
> zorn@dms-1.ana.bna.boeing.com
> 
Mike,

Rollforwarddb requires a configuration file (aaaaaaaa.cnf) to operate.
Ingres has 2 of these for each database - one in the data location and the
other in the dump location.  The config file is updated with details of
the checkpoint when the checkpoint completes.  However, ckpdb copies the
config file as it exists at the time a checkpoint commences.  If you have a
failure which causes both the config files on disk to be lost then you
cannot run rollforwarddb.  If you are running online checkpoints then
you also need dump and journal files preserved to perform a rollforwarddb.
Therefore, to cover against loss of the entire system or multiple disks
you need to have the checkpoint tape, the config file, dump file(s) and
journal files as at the time of checkpoint completion.

-- 
Gavin Trigg	Email: G.Trigg@its.unimelb.EDU.AU
		Telephone: +61 3 9344 6003 	Fax +61 3 9347 9273
Manager Administrative Systems Processing, Information Technology Services,
The University of Melbourne, Parkville, Australia.  3052.




 wrote:

>   I find references now and again to aaaaaaaa.cnf (principally in Mike
> Leo's Ingres World 95 paper "Safe & Recoverable CA-Openingres Database
> Backup").  He says to back up that file as a separate item (because the
> a*.cnf on the backup tape isn't valid for the tape [for what then?].
> 
>   The DBA Guide, Ch 16, makes no mention of that file.  So then, do you
> really need a separate backup of a*.cnf (and are the Ingres manuals
> overlooking something)?

The point is, during the checkpoint file-copy the aaaaaaaa.cnf file
stored as part of the checkpoint is worthless.  That's because it isn't
updated with the checkpoint results until AFTER the checkpoint file copy
completes.
So what you want to do is make a separate copy of aaaaaaaa.cnf from
either the data area, or the dump area (which has a copy of aaaaaaaa.cnf),
or both.

As long as you have a safe copy of a POST-COMPLETION aaaaaaaa.cnf somewhere,
you can screw up a recovery attempt and you get to try again.
If you don't have a safe copy, you get one shot, and maybe not even one.
I found that discovery to be pretty motivating... :-)

Karl
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