Re: optimizer and MTS

On Jul 4, 11:01 am, "Syltrem" <syltremz..._at_videotron.ca> wrote:
> "Mark D Powell" <Mark.Pow..._at_eds.com> wrote in messagenews:1182865465.802870.322410_at_n2g2000hse.googlegroups.com...
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>
>
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> > On Jun 26, 4:05 am, sybrandb <sybra..._at_gmail.com> wrote:
> >> On Jun 25, 11:11 pm, wagen..._at_yahoo.com wrote:
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> >> > Oracle 9.2.x
> >> > solaris 2.7
>
> >> > Does MTS in anyway influence the optimizer?
>
> >> > I think the answer is NO, but just wanted to get some input.
>
> >> > Thanks
> >> > wagen
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> >> The answer is NO. MTS is just a connection mechanism.
> >> Be aware though you can't trace a MTS connection, as there is no
> >> guarantee the entire session will be executed by one shared server
> >> process.
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> >> --
> >> Sybrand Bakker
> >> Senior Oracle DBA
>
> > I would like to point out that MTS is an obsolete term in 9.2 as
> > Oracle refers to this feature as Shared Server now.
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> > With version 10g Oracle provides a utility for combining trace files
> > to aid in tracing Shared Server processing; however, unless your
> > system is near its limit on how many processes it can fork you should
> > consider switching back to dedicated sessions.
>
> > There is a performance penality for using Shared Server and using
> > Shared Server does not reduce OS memory requirements since you have to
> > increase the shared pool size to support the Shared Server processing.
>
> Yes it does reduce the memory requirements.
> I started using it in 9i for this exact reason. With many new web users
> connecting, I memory was starting to be a problem. It reduced page faulting
> dramatically on this server.
> Not all sessions are active at the same time, and in average they use less
> memory than dedicated servers
> That's true for OpenVMS anyway.
>
> There is some overhead associated with shared servers, but so far this has
> not been perceived by the users.
> But I continue to have batch jobs connecting to dedicated servers, only
> interactive users and web are on shared servers.
>
> Regards,
>
> Syltrem

It's my observation (not supported by any evidence, just from watching this group and elsewhere) that VMS and Windows servers seem to benefit from the option, but unix doesn't. The docs do say it's a scalability device, not a performance device. It may also be more appropriate on n-level architectures where there is no instrumentation to place blame.

Of course on unix, I've seen a number of installations that benefitted from throwing it out.

jg

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