How do you hot-backup ORACLE?

[Randy Hagedorn]

Hi,
I am looking to see what backup utilities people are using to Hot-Backup ORACLE.

We use fbackup and even though we are in hot-backup mode, updates can still occur to datafiles and control files and thus fbackup detects the change and will not backup the files.

So, I was wondering what other people's experiences are?

Thanks in advance.
Dewy

[James R. Ferguson]

Hi:

You can use utilities like 'fbackup' to backup and Oracle database, but you need to alter your tablespace to begin and then end "backup" mode; something like:

alter tablespace $TBLSPACE begin backup
...(do your backup)
alter tablespace $TBLSPACE end backup

Regards!

...JRF...

[Randy Hagedorn]

JRF,

We are altering our databases with the begin backup and end backup procedures. But fbackup will still skip the datafiles, because updates still occur during the backup and thus fbackup skips it.

Part of my question, is that, is fbackup capable of cleanly backing up the data or do I need a third-party utility?

Thanks, Dewy

[Leif Halvarsson_2]

Hi

Which Oracle version do you use. In Orace 8 and later is a utility "RMAN" for high performance online backups which can be used "standalone" but also together with a 3-party backup program (as OmniBack) for media mangement.

[Randy Hagedorn]

We are on ORACLE 8.1.7

[Dave Chamberlin]

We use omniback to do our hot and cold backups. The pre-exec script puts things in backup mode, the post-exec script returns them to normal. Works well for us.

[MANOJ SRIVASTAVA]

Hi Dewy

Essentially waht hapeens when u put the database in abckup mode is that the users still use the database bu the modifications are stoerd in the archive logs , and the real data is not modified . When you take the Database out of the backup mode the oracle applies the logs back to the real data and brings it online , This enables the suer to sue the database even if the backup is being taken . Please note the backup has to complete soon and the archive logs become huse and then it takes longer to revert back.


Manoj Srivastava

[Jeanine Kone]

I'd have to say that you should be able to use fbackup. I have used it for mine without any problems.

[Randy Hagedorn]

Here is an example of the fbackup warning we get.

22: /u03/oradata/ORD/user03.dbf 1536016
23: /u03/oradata/ORD/user04.dbf 1536016
fbackup(3009): WARNING: File number 23 (/u03/oradata/ORD/user04.dbf)
was not successfully backed up

Does this seem to be a hot-backup issue?

Thanks

[A. Clay Stephenson]

Are these files part of the tablespace that you did the alter tablespace on? Fbackup has detected that these files have been modified since the backup started.

Let me also mention a Plan B. You could shutdown the database, make OnlineJFS snapshot mounts of the Oracle filesystems, and restart the database. This operation will take about two minutes typically and your users can go back to work. You then do your backups on the snapshot mounted filesystems. You have almost all the benefits of a hotbackup with the safety and security of a cold backup. When the backups are finished, you unmount the snapshots.

[Randy Hagedorn]

Yes, these are the tablespaces that we are altering to backup mode.

Another thought I had was to use our MirrorUX to do a split-mirror backup, off of the mirrored copy of our data.

I think we would still need to alter the tablespace into backup mode prior to the split, so that we would get an ORACLE checkpoint.

[T G Manikandan]

Recovery manager(RMAN) is a great tool for Oracle backup's.
It has several features like

1.you can look for block corruption.
2.Incremental backup
3.It can recover files without prompting you any date ot file.It has its own catalog.
4.The information in the catalog can be easily queried using reports and lists.

It can be integrated with the third party media management software like Legato manager to get wonderful results.


Thanks

[T G Manikandan]

I just forgot to put in the main point

RMAN does not backs up only the used space of the database.
Also RMAN does not put the tablespace in backup mode thus saving redo overhead.
It re-reads the database blocks until it gets a consistent image of that.

Also parallel backups are possible with RMAN.

[T G Manikandan]

Sorry for the last answer.

---It just backs up the used space on the database.
-----
It is late night here.infact early morning.
I have posted a query and waiting for replies from the great admins.

Sorry

Thanks

[Mark Seaman · Accepted solution]

Starting with 8i, Oracle introduced 'ALTER SYSTEM SUSPEND/RESUME' to freeze I/O on the server. You put the tablespace(s) in backup mode, execute this command, wait for a while, and then perform your backup. Since all I/O is frozen, this technique should only be used for some very quick method of backup like split mirror or snapshot. I say 'wait for awhile' because there is currently no way to tell that I/O has ceased.
Another option might be the Freeze/Thaw ioctl()'s for vxfs file systems. These flush buffers and freeze I/O synchronously, so you are guaranteed to have no I/O when they return.
Contrary to what others have said, Oracle continues to write to datafiles during backup mode. The SCN in the datafile header is frozen during hot backup, to ensure redo is applied when the recover command is issued. As long as you have the redo generated for the entire time the tablespace was in backup mode, you are guaranteed to be able to recover a consistent copy of your datafile. This is true as long as you as you have not turned off the _log_blocks_during_backup initialization parameter.