Hi Tracy,
Oracle still won't let you do a fast refresh if the
creation time stamp on the snapshot log is more recent
than the creation time stamp or last complete refresh
of the snapshot. An attempt to do so will generate
the dreaded ORA-12004: "REFRESH FAST cannot be used"
(see note 1035524.6 "DIAGNOSING THE ORA-12004").
The bottom line is Oracle has to guarantee that
snapshots will be in sync with their master tables and
the only way it can do that is to prevent you from
doing something that could potentially allow them to
get out of sync.
You don't mention what version you're on, but if
you're on 8i and using PK-based snapshots, why not
alter the master table storage conditions and use
ALTER TABLE ... MOVE to move it into the new
tablespace? I haven't personally tried this, but I
don't see why it wouldn't work.
I was also trying to think of a way the ON PREBUILT
TABLE clause of the create snapshot/MV command in 8i
could be used, but you'd still have to end up
exporting/importing the table on the snapshot site or
recreating it in some fashion (CTAS, sqlldr, etc...)
as it will complain about the snapshot already
existing and if you drop it you've lost the base
table.
HTH,
- Anita
- Tracy Rahmlow <Tracy.Rahmlow_at_aexp.com> wrote:
> Hi Anita,
> Ironically that is just what I am trying to do. (ie
> implement a storage plan
> which will address the issues discussed in the
> paper) To your other point, I
> understand oracle's position, but if I can prohibit
> changes to the master
> during the reorg/rebuild, is this still an issue?
> ---------------------- Forwarded by Tracy Rahmlow on
> 05/31/2001 12:37 PM
> ---------------------------
>
> From: "A. Bardeen" <abardeen1_at_yahoo.com>@fatcity.com
> on 05/31/2001 04:51 AM PST
>
> Please respond to ORACLE-L_at_fatcity.com
>
> Sent by: root_at_fatcity.com
>
>
> To: "Multiple recipients of list ORACLE-L"
> <ORACLE-L_at_fatcity.com>
> cc:
> Subject: Re: Snapshot Logs Explanation Needed
>
>
> Tracy,
>
> You may know that there were no modifications to the
> master table made from the time the snapshot log was
> dropped until it was recreated, but Oracle can't
> take
> that chance, otherwise data could get out of sync.
> That's why you have to either recreate your snapshot
> or do a complete refresh if the snapshot log is
> recreated.
>
> To avoid recreating the snapshots I would ask why
> you
> need to reorg your master tables (i.e. what do you
> hope to accomplish by this)? If you're doing it for
> defragmentation reasons, I suggest you check out the
> excellent white paper "How to stop defragmenting and
> start living..." to see if this is really necessary.
>
> http://www.vampired.net/articles/files/stopfrag.zip
>
> HTH,
>
> -- Anita
>
> --- Tracy Rahmlow <Tracy.Rahmlow_at_aexp.com> wrote:
> > I would like to reorg many tables which have
> > snapshots associated with them. I
> > understand that if the master table is dropped the
> > snapshot log is also
> > dropped. When a log is dropped, oracle states
> that
> > you need to do a complete
> > refresh of the affected snapshot. My question is
> > why? If you do not allow
> > users to access the database with the master
> table,
> > then you should not have
> > any transactions that would be lost. Why can't
> you
> > create a new log and
> > continue to do a fast refresh? I am trying to
> > avoid having to recreate all
> > the snapshots due to the size and number that we
> > have. Any thoughts? Thanks
> >
> >
> > --
> > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.com
> > --
> > Author: Tracy Rahmlow
> > INET: Tracy.Rahmlow_at_aexp.com
> >
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Received on Thu May 31 2001 - 15:36:08 CDT
