Re: rman backup slow

From: Prasad <>
Date: Sat, 31 Jan 2009 22:02:31 -0800
Message-ID: <>

Hi Robert,

I did as you suggested with no catalog . it took 30 minutes for a 8GB datafile .which
still doesnot look that good ?

There is no major db size change in last few quarters . it is just that recently it is
overlapping with the business hours once in a while.

The backup goes to one disk device . we are using 2 channel . I have yet to find out the disk io far I have been trying from Oracle side to see if any improvement can be done.

The current current vxfs fs does not support async_io . as the way for us to make it use
async io is to use ODM or quick i/o and both are not easy option at this time for this 9i database so hoping enabling multiple slave will reduce async io wait.

Pleae let me know if I miss anything.


On Sat, Jan 31, 2009 at 4:42 PM, Robert Freeman <>wrote:

> Do a backup without the catalog. Does it go faster? You can start by just
> testing the backup of a specific datafile with and without the catalog,
> rather than the whole database. I'd do one that is big enough to give you a
> decent backup run time.
> Has this database gotten bigger over time or is it's size static? Is the
> increased run time of the backup related to any increase in database size?
> Are you just backing up to one disk device? Are you using one channel or
> multiple channels? What is the disk IO rate for writes in ms? Are you
> getting the throughput you need on your disks.
> I would not change the parameters you are talking about just yet. It would
> be much smarter to figure out for sure what is causing your problem before
> you change lots of parameters and potentially make the problem even worse.
> I assume that your system does ASYNC IO? Correct? I would not go the SYNC
> IO path as you are suggesting by setting disk_asynch_io to false.
> RF
> Robert G. Freeman
> Author:
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> (Sybex)
> Oracle Database 11g New Features (Oracle Press)
> Portable DBA: Oracle (Oracle Press)
> Oracle Database 10g New Features (Oracle Press)
> Oracle9i RMAN Backup and Recovery (Oracle Press)
> Oracle9i New Features (Oracle Press)
> Other various titles out of print now...
> Blog:
> The LDS Church is looking for DBA's. You do have to be a Church member in
> good standing. A lot of kind people write me, concerned I may be breaking
> the law by saying you have to be a Church member. It's legal I promise! :-)
> ------------------------------
> *From:* Prasad <>
> *To:* ORACLE-L <>
> *Sent:* Friday, January 30, 2009 9:45:46 PM
> *Subject:* Re: rman backup slow
> my apologies for the late response. To answer this . not it is not a
> new database . it has been in production since last couple of years. it
> hosts a application which has lot of LONG RAW data . it is right now 170GB .
> out of which the LONG RAW table only occupies 80GB. The RMAN backup is
> taken connected to recover catalog . The backup goes to disk . right now
> the cursor_sharing is set to similar . The most significant wait I see is
> disk async i/o . This is a solaris server with vxfs and it do not support
> async i/o .
> The puzzling factor is the select on x$dual which just sits silently for
> hours. and the entire backup duration goes beyond 10 hour .
> This is what we are planning to do increase the db_writer_process from 1
> to 4 and set the disk_asynch_io to false ( i gues the default is TRUE) .
> would appreciate your thoughts on this change .
> because of the sensitivity of the application ( it is a highly visible
> production database) it is a bit hard to find time to take a no catalog
> backup and also do any tracing experiment . but i guess it seems
> unavoidable .
> hopefully I didnt miss to provide any information asked. please feel free
> to let me know if any further information will assist finding solution.
> Thanks again .
> thanks
> Prasad
>> On Jan 30, 2009, at 1:10, Prasad <> wrote:
>> All,
>> we have a 170G db on 9) . and I see that it currently is
>> taking nearly 10 hour+ to do a rman backup . when I see this in grid
>> control I see the rman session keeps waiting on this sql .
>> anyone has any similar situation . appreciate any suggestion.
>> Thanks in advance
>> thanks
>> Prasad

Received on Sun Feb 01 2009 - 00:02:31 CST

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