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
Correct.
By the way: A good rule is to always keep the sequence Table - Snapshot Log -
Snapshot, ie. don't break the sequence, for instance by dropping and
re-creating the snapshot log. If something happens to the snapshot log you
should drop the snapshot, create the snapshot log, then re-create
If you do a snapshot refresh then the snapshot log should be empty(correct?).
Then I would think you could reorg the master table as long as you prohibit
users from updating the master until the reorg and the recreating of the log is
complete. Thus eliminating the need to do a complete refresh
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?
If you do a snapshot refresh then the snapshot log should be empty(correct?).
Then I would think you could reorg the master table as long as you prohibit
users from updating the master until the reorg and the recreating of the log is
complete. Thus eliminating the need to do a complete refresh
]
To: Multiple recipients of list ORACLE-L
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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
OK, checked TFM and there are two type of fast refresh snapshots: primary
key (new in 8)
and rowid.
For a rowid snapshot, when the table (EMP) is updated, a row is added to the
snapshot log (MLOG$_EMP) containing mainly the type of action, timestamping
info, and the rowid (MLOG$_EMP.M_ROW$$) of
Been a while since I worked with snapshots, but if I remember correctly,
each record in a fast refresh snapshot keeps a mapping back to the rowid on
the master. If you drop and recreate the master table, the mapping is hosed
and updates/deletes do not propagate to the snapshot.
Brian Norrell
