David - I am running exactly the same tsm and OS/390, but with mpthreading on.
I haven't seen any problems caused by it.  I turned it on at the suggestion of
tsm level 2 support to fix a pmr, I don't remember what the problem was.
I have just one processor, but level 2 assured me it would help anyway.

Bill

At 03:10 PM 5/14/2002 -0400, you wrote:
>We are running OS390/2.10 with TSM 4.2.1.9 currently we have MPTHREADING
>set to NO.
> I was considering changing it to yes. Has anyone had problems with the
>MPTHREADING?
>Also, what if any improvements can I expect?

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Bill Colwell
Bill Colwell
C. S. Draper Lab
Cambridge Ma.