Re: Materialized View Log - ??

"Timothy Madsen" <timothy_madsen_at_bigfoot.com> wrote in message news:b7jj3m$cup$1_at_bob.news.rcn.net...
> Hello,
> Well - that is pretty much why I am asking...
> :)
>
> I have done rather extensive testing and have implemented a solution to a
> particular problem which required a trigger to be operating on the COMMIT
> operation. The triggers on the MV tables are now firing when the COMMIT
> occurs. I specifically did not execute any creation script for the MV
log -
> and I have checked with both Quest Schema Manager and Quest SQL Navigator
to
> see if the MV logs were somehow created automagically for me - behind the
> scenes - I do not see them.
>
> So, I am pretty confident (although as always - I could be wrong) that:
> 1) My triggers on my MV tables are firing during the COMMIT and
> 2) I have no materialized log.
>
> Note that I started using these MV from an example from Thomas Kyte
> (asktom.oracle.com) which did not include the creation of a materialized
> log.
>
> So, I was wondering of what purpose the MV logs are and under what
> circumstances one is required to use them?
>

Hi Tim,

Not entirely sure I follow but here goes ...

In order to perform a fast refresh a MV, without the need for any explicit "triggers" (which I don't quite follow what you mean) you must have a MV log. The log effectively contains all the "changes" made to the master table and some form of identification (rowid / primary key) so it knows where to apply the changes.

Upon the refresh (either through a commit, when scheduled, manually etc) Oracle only need apply the changes since the last refresh rather than the alternative which is to completely rebuild the MV.

No MV log, no fast refresh.

Cheers

Richard Received on Wed Apr 16 2003 - 08:59:05 CDT