Just something. First of all, I have never seen Shareplex in operation
so this is my gut feeling, chiefly based on how I would have coded it.
Most of the arguments against Shareplex has been about their using
undocumented features - which I admit may be a concern but wouldn't keep
me awake at night. The main difference I see between log-based
replication and traditional, trigger-based replication is that with
trigger-based replication the log is part of the transaction - in other
words, you only see committed changes. With the logs, the picture is
different, because you may have uncommitted as well as committed changes
in them - you are a bit closer to what people do. Either they wait for
transactions to have committed before forwarding them - which I think
unlikely because at the first massive update they can go BANG, if what
happens to rollback segments from time to time is anything to go by, or,
and that's how I would have done it, they forward changes as they come,
forwarding commits and rollbacks as well. And in my view, the problem is
not on the source, but on the target side. I presume that one, or in the
best of case, a limited number of sessions are replaying the original
changes; if you have many concurrent sessions on the source, you have a
kind of funnelling. Because of Oracle read consistency, the original
transactions, if they are working on the same data, may not see exactly
the same thing at the same moment. Oracle locks take care of that, but
if you multiplex everything I do not see how to keep a consistent
picture at the other end, even when strictly respecting chronology. A
secondary, and relatively minor compared to the first one, concern would
be what happens if a replication process crashes (I know, it's not
supposed to happen) and if this is not spotted immediately? I presume
that ARCHIVELOG is mandatory, but anyway you must probably have tight
operations. It must be perfect for some operations, but I would feel
uncomfortable using it on the case-study OLTP database.
My 2 cents.
St�phane Faroult
"Rao, Maheswara" wrote:
>
> List,
>
> My company is considering Quest - Shareplex.
>
> We are considering to use this in our dataware house. Basically, this will
> pull all the transactions from OLTP database and populate staging area in
> the dataware house.
>
> Could you please give your experiences and the pros and cons of this
> Shareplex product.
>
> Thanks,
>
> Rao
> --
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