The best db backup way to decrease online backup time?

[Former Member]

Hi Gurus,

It may be a common question: since data volume grows bigger and bigger, oracle db full backup time also gets longer and longer, now it reaches about 21 hours for 4TB. Does any guru know a way to backup safely and taking as little time as possible?

Oracle incremental backup is of course available, but is its recovery safe and correct and riskless?

Or I remember there is some harddisk mirror tech： B is mirroring A all the time when a backup is started, they split temporarily and then B is taken to be backuped up. When finished, A and B resumes mirroring again. In that way, it is actually an offline backup, and A almost stays working all the time.

Does Oracle have this kind of technology to support? Hope to get your answers soon!

Jennifer

[stefan_koehler]

Hello Jennifer,

nice to hear that you are using RMAN )

It is really important to know, which backup medium you are using (RMAN with backup to disk, RMAN with backup to tape or RMAN with MML (for example TSM)). Also we need to know the available resources on your backup side.

At first you need to identify the bottle neck by your backup - for example:

• CPU bound on database host

• I/O bound on database host

• Network bottleneck by copying the data to backup medium (if you are using TSM for example)

• I/O bound on backup side (maybe the tapes, disks, etc.)

If you have checked all these components and don't find any bottleneck, then you will have to parallelize your backup - this can also be done with RMAN very easily. The parallel degree also depends on your hardware and the available resources. But keep in mind the memory allocation of oracle by RMAN Backup ([RMAN Memory|http://sysdba.wordpress.com/2007/05/08/how-to-calculate-the-minimum-size-of-large_pool_size-for-io-slaves-rman-and-memory-utilization/]).

Just to tell you some values:

We are performing a parallel backup of our production system (round about 4.2 TB) with TSM and a LAN-free agent (data is directly written on tape - not through the network). The backup needs round about 4-5 hours.

> Oracle incremental backup is of course available, but is its recovery safe and correct and riskless?

Yes it is in my experience. With Oracle 10g you have also a nice feature called "Rolling Forward Image Copy Backups", which gives you the possibility to reduce the restore time, because of the incremental backups are merged into the full backup automatically.

You can also use "Block Change Tracking" to reduce the I/O load by an incremental backup.

Regards

Stefan

[Former Member]

You could also buy a faster backup solution. In the place that I´m right now they do PRD backups of 7.3 teras in two and a half hour using LTO4 and parallel procesing (that's what I was told).

Also remember that tape drives are the main cause (usually) for slow backups so why don´t you take backups to disk first and then move those files to tape? That´s one of the recomendations I have heard from specialists in Backup/Restore solutions. This one has the advantage that if you ever need to recover the DB then you already have it on disk so it will be faster to recover from a bad situation.

Good luck

[lbreddemann]

Dear Jennifer,

there are plenty of options available, including a 'split-mirror' backup (which is fully supported by the BRTOOLS).

A good starting point for your research likely is SAP note "842240 FAQ: Backup strategy of large and highly-available databases".

Since most customers still seem to favour the classic file-copy approach for Oracle backups I would start by implementing RMAN instead and check how long the backup is taking with that.

best regards,

Lars

[Former Member]

hi Lars,

we've already usde RMAN, still taking so long time to backup.

[former_member204746]

what method of backup are you using?

BRBACKUP?

BRABACKUP with BACKINT?

RMAN?

RMAN with BACKINT?

OS backup?

are you using a tape library?

if using BACKINT, what product are you using?

Are you on a SAN? if so, which model?

what is your OS?

[Former Member]

Hi Eric,

we are using RMAN, our OS is Unix.

[former_member204746]

you have not answered these 2 questions:

are you using a tape library?

Are you on a SAN? if so, which model?