Re: RMAN

It's always nice to have the right tool for the job... RMAN and OS-based hot backups have complementary strengths and weaknesses.

In other words, to make a "business case for RMAN" does not exclude retaining OS-based hot backups!!

If you are only interested in disaster recovery, where for every thousand backups you make, you hope to actually use zero or at most one of them, RMAN is probably the best bet.

In my job, I am frequently asked to copy databases from machine to machine, over WAN links, in order to support ad hoc reporting, development, system integration, etc. Export/import is way too slow for this, so restoring backups becomes the method of choice.

These machines do not always have the same file system configuration or space (even using OFA, a symbolic link cannot make your filesystem suddenly double in size!!). Hot backups make it fairly easy to relocate data files to different directories (using backup controlfile). (I finally figured out how to do the same thing with RMAN using the "auxiliary" database but it was a pain, certainly no easier than doing it via a shell script and an OS-based hot backup).

Hot backups require less space overhead -- I can locally restore a 10GB database with only 11-12 GB of free disk space available, by un-zipping each datafile into place. To do the same with RMAN would probably require 15-20 GB, depending on how much empty space is in your DB -- because you have to be able to store all the unzipped backup files and the newly restored DB all at the same time.

Yes, yes, I know disks are cheap (on some platforms, anyway...) -- but after you put five or six copies of a 15 GB database on one machine, you're starting to annoy the people who have to install, configure and pay for more disks.

And last but not least, an OS-based hot backup script would probably be easier for a Unix admin to maintain and trouble-shoot than RMAN. This may be a factor if you're working a 24x7 on-call schedule with both Unix and Oracle folks involved. (For MS-Windows, ignore this...)

--Mark B.

Scott wrote:

> The site where I work is looking into RMAN as a future possibility.
> What I need to know from the DBAs out there is are you using RMAN ? If
> so why and what is it's biggest plus? Any drawbacks ?
>
> If you're not using RMAN, why not ? Is it based on any drawbacks ?
>
> And Have you had any problems with RMAN that could not be addressed
> and fixed ?
>
> How many of the past companies you worked for used RMAN ? And how many
> companies you worked for did not use RMAN ?
>
>
> Please send all replies to : gruber_at_mac.com, I'm trying to come up
> with a business case for RMAN. Thanks for all your input in advance,
>
> Scott Gruber
> Senior UNIX Systems Administrator
>
> ( Even though I'm a Systems administrator I have used RMAN in the past
> and I think it is a great backup/recovery tool )
>
Received on Fri Feb 08 2002 - 20:10:30 CST