Re: RMAN v Control Files

On Sat, 15 Feb 2003 22:46:29 +0800, Gary Mandaracas wrote:

> Can anyone advise,
>
> We have installed HP's Data Protector to backup our Oracle databses and
> other systems in two of our sites and been given different advise by
> consultants working on each installation.
>
> For Data Protector you can configure the backup to integrate with RMAN or
> make use of Control files. In the first install we where advised to
> configure RMAN prior to the consultant coming in to install and set-up the
> backup software, however in a more recent install at another site the
> consultant advised us to make use of the Control files.
>
> Is he cutting corners to get the job done or does it really make no
> difference? What are the pros and cons of each approach?
>
> Any advice would be appreciated.
>
> Gary

It's not entirely clear what you are talking about, because I don't know the specific product you mention but I *think* you are saying that one consultant advised the use of a Catalog Database for RMAN to use as its repository, and another advised not to bother with a Catalog Database at all, but get RMAN to store its repository information in the Control Files of the target database itself. (I'm assuming that this Data Protector is just an HP fancy front-end for RMAN. Ignore the rest of this post if that's not the case).

If that is a fair summary of what you've been advised, then my view is that it's the one recommending the use of a Catalog Database that needs to get up to speed. There is little need for one in 9i, unless your backup strategy is complex, your backup volumes are high, or you have some other weird backup requirement.

However, it does mean that RMAN will be storing stuff in your control files. Firstly, that makes the control files get bigger -though not by much -maybe 60MB or so. Secondly, you need to make sure that you never, ever lose all copies of your control files (multiplexing is easy, ought to be compulsory, and does the job nicely... and I mean multiplexing, not hardware mirroring, though you can do that as well). Having said that, if disaster strikes and you *do* lose all copies of your control files, then recovery is still possible, provided you make sure that you configure RMAN's automatic backup of control files feature (which mysteriously and very stupidly defaults to being off!). Thirdly, make sure the control file retains records long enough to cope with 'odd' recoveries: the default is for the control file entries to begin to be over-written after 7 days, but that would potentially mean it was impossible to perform an unusual recovery from a backup taken 8 days ago. Use the init.ora/spfile parameter CONTROLFILE_RECORD_KEEP_TIME to bump up the number of days to something appropriate for you.

There was a 'fourthly', but I've forgotten what it was!

So I'll leave it there, particularly since none of this might actually apply to this HP product.

Regards
HJR Received on Sat Feb 15 2003 - 16:39:30 CST