RE: Backups on raw devices

With Oracle 8.0 there was RMAN functionality that you could only get by having a repository in a database. But with Oracle 8.1 it seems that you get all the functionality you need with controlfiles. What functionality do you lose by using RMAN with controlfiles?

Steve Orr

-----Original Message-----
Sent: Monday, June 18, 2001 2:11 PM
To: Multiple recipients of list ORACLE-L

You can just use the controlfile so you don't have to setup a database repository. Here's a clip from page 2-8 of the User's Guide:

"When you use a control file as the RMAN repository, RMAN still functions very effectively. If you choose not to use a recovery catalog, follow the guidelines in "Managing the RMAN Repository Without a Recovery Catalog" on page 3-45. Specifically, make sure you understand which commands require a catalog, and develop a strategy for backing up the repository."

You can configure the amount of history kept in you controlfiles with the following init.ora entry:
# Keep 14 days of history in the control file for the RMAN backups... CONTROL_FILE_RECORD_KEEP_TIME = 14 Of course, make sure you backup the controlfiles. :-)

Steve Orr

-----Original Message-----
Sent: Monday, June 18, 2001 9:17 AM
To: Multiple recipients of list ORACLE-L

I've logged a TAR on this one with Oracle. They have verified what I suspected all along. The SAs here don't understand how Oracle performs a hot backup. There is no difference between raw and cooked file systems as far as Oracle is concerned when performing a hot backup. Also, the skipping of the header is only applicable to certain variants of UNIX.

One other question here. Does anyone have recommendations on the repository database required for RMAN? Do we need to keep a separate instance on another production box? Or the same production box? Does everybody have all of there repository information for all of their database in one instance? It seems like you would want a separate instance for each repository and have them staggered across different machines so that the odds of losing your database and it's repository at the same time would be low. Any suggestions?

Thanks for all the replies so far!

--Michael

-----Original Message-----
Sent: Friday, June 15, 2001 9:55 PM
To: Multiple recipients of list ORACLE-L

Michael,
 We use RMAN on RAW with EDM (EMC) backups, without any problem. When using RMAN, it will take care of all blocks that are being changed while the backup is
going on. Also as EDM interfaces with the Tape library, RMAN will write directly
to the Tape . Have this set up on about 15 databases and all of them are working
fine. But occasionally our backups fail on 8.1.6 databases due to lack of resources on the Server (and some bugs!).

Rama

"Jenkins, Michael" wrote:

> We have parallel server running on on a Sun Cluster 2.2 and we are looking
> for the easiest way to perform hot backups. Now, I know that you have to
> use the "dd" command and skip the header at the beginning. Everything I
> read on metalink indicates that you can use basically the same paradigm as
a
> hot backup on cooked file systems. But, the sysadmins here tell me that
the
> raw device can't be backed up if there is any write activity on the data
> file that is currently being backed up. Now we all know that contrary to
> popular belief there is write activity on a data file even when the
> tablespace is in backup mode. Is "rman" or some other block-level backup
> utility the only way to get a reliable hot backup on raw devices? Does
> anybody have any experience with hot backups that are made while the
> database still has active users logged in?
>
> I look forward to everyone's thought on this.
>
> Thanks.
>
> Michael L. Jenkins
> Oracle Certified DBA
> Nextel Communications
> Norcross, GA
>
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