Since this thread got into opinion I'd like to know if anyone has any
opinions yet on using Oracle-managed undo in 9i. Oracle's opinion is that
they strongly recommend it but.... any thoughts?
"Ricky Sanchez" <rsanchez_at_more.net> wrote in message
news:3BE1CF33.2EE9C604_at_more.net...
> Leigh-
>
> This is one of those questions that turn into hair-splitting discussions
> rather than focus on the larger picture. The contention issue with
> dictionary managed tablespaces is with the ST enqueue, of which there is
> exactly one for the database. Steve mentions increased IO to access a
> couple of views, but that IO is read-only and cannot cause ST enqueue
> contention. A bit of IO to peek at segment and extent status is trivial
> in any case. I don't think his argument can be generalized
> intelligently.
>
> I have a hard time understanding the last Q & A. The answer indicates
> having inherited a database with dictionary managed TS for temp and
> rollback and LMT for data and index. This would seem to be a nearly
> worst-case scenario. Temp and undo are most often busy with extent
> management and are the best candidates for LMT. In any case, it does not
> answer the question asked. Maybe this is presented out of context or
> something.
>
> I think the correct answer to the question asked is "you do want to use
> LMT whenever possible. It presents a nice, generalized solution to
> extent management and enhances performance in nearly every case. Any
> case you can find for which LMT is not a good solution is probably
> fairly exotic and beyond the grasp of most DBAs anyway."
>
> I also noticed a comment suggesting system tablespace should always be
> dictionary managed. Silly rationale and no logic is offered to support
> it. LMT makes sense, so use it when you can. Soon enough, it will be the
> only option anyway, so you might as well get used to it.
>
> just my two pesos...
>
> - ricky
>
> Leigh wrote:
> >
> > Does anyone agree/disagree with Steve's synopsis of locally managed
> > tablespaces particularly that they can cause much more physical IO
> > than dict managed for tablespaces with many small segments? Has
> > anyone had any significant improvment after using them on moderately
> > sized databases - eg. 10 - 20GB or any phobia of using them?
> >
Received on Thu Nov 01 2001 - 19:00:11 CST
