Re: restore q from TSM
Date: Sat, 26 Feb 2011 10:09:43 +0000
Message-ID: <77062DA5-814F-482C-B050-75D2DB0D3C4E_at_vishalgupta.com>
Same applies to multiple TDP channels from single server as well. Each rman channel via TDP is treated by TSM as separate TSM session. So if rman decides to restore from multiple backup pieces in multiple channels and these backup pieces are on same tape, then other channels will to have to wait for tape to be free from first channel.
And usually every TSM is configured to stored backups above a defined threhold size, first on staging disk pool, then they offstage from staging disks to tape in the background. And your multiple backup pieces backup at the same time end up on the same tape. Since TSM does not many tape heads ( it may have between 1 or 10 tape heads) and you may have multiple clients trying to backup at the same time. So in order to optimise this TSM temporarily stores backup on staging disk first and then moves them to tape. Staging disks are usually few TB in size but they do get filled up at a faster rate than the rate at which data can be destaged.
So any backup file above defined and configured threshold goes straight to tape bypassing the staging disk pool.
Just few of things to keep in mind with Tape backup servers.
Cheers,
Vishal
On 25 Feb 2011, at 18:27, "K R" <kp0773_at_gmail.com> wrote:
> Thanks Vishal .
>
> On Wed, Feb 23, 2011 at 1:46 AM, Vishal Gupta <vishal_at_vishalgupta.com> wrote:
> If backups are stored on tape in TSM, then even if you start restore of database to 5 machines, other sessions will have to wait as backup stored on tape are being restored by first session and first session is holding the tape. TSM does not allow more than one session to access the same tape ( tape being serial access medium) at any point in time. Though if TSM was using VTL (virtual tape library) which holds backups on disk on TSM server, then you could restore to multiple machines at the same time. Because disk is a random access drive unlike tape which are serial access drives.
>
> Cheers,
> Vishal
>
> On 22 Feb 2011, at 16:53, "Peter Hitchman" <pjhoraclel_at_gmail.com> wrote:
>
> > Hi,
> > I do not have much TSM admin background either! But TSM may have been
> > set-up so that you will only be allowed so many tape mounts possibly
> > per session connecting to TSM and probably a TSM global maximum
> > setting as well, which will probably be the number of tape drives you
> > have. Sorry but you really need to talk to your TSM admin, if such
> > exists, or if that is you, look much more deeply into TSM admin.
> >
> > Regards
> > Pete
> > --
> > http://www.freelists.org/webpage/oracle-l
> >
> >
>
>
-- http://www.freelists.org/webpage/oracle-lReceived on Sat Feb 26 2011 - 04:09:43 CST