Brian,

We've actually been thinking about this too, as we evaluate moving to z14's. We 
currently have a 5 member GRS ring that could really benefit moving to GRS 
Star,  but nobody want's to spend any $ for an ICF.

As of BC12 generation IBM was still recommending against using GPs for CF 
processors:

According to an IBM paper titled:  Coupling Thin Interrupts and CF Performance 
in Shared Processor Environments

While it is possible to use general purpose processors, CPs, as CF processors
and share the CPs with z/OS and other similarly defined CFs, this is not a
recommended configuration. Using CPs as CF processors creates interaction
between z/OS and the CF in terms of cache reuse and other factors that may
impact performance. 

Dana


On Tue, 29 Jan 2019 00:23:56 -0600, Brian Westerman 
<[email protected]> wrote:

>Hi,
>
>Has anyone had any experience with using the internal coupling channels on a 
>z13.  "supposedly" IBM has removed the active wait problems (where the CF lpar 
>would try to use 100% of whatever it gets from PR/SM), but I was wondering if 
>it's ready for prime time yet.  I have a z13s (single CPU) with 3 LPARs on it, 
>they are fairly low use, but I think it'a about time the started to use GRS 
>since they share DASD (it was small, but now more and more as time goes on).  
>They have been lucky so far, but I would rather not rely on luck.  They don't 
>have the cash to add a specialty processor, and if IBM has really reduced the 
>overhead of ICF, then it might be a good fit for them.
>

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