On Mon, 21 Apr 2014 07:01:50 -0500, Tom Marchant wrote:

>On Fri, 18 Apr 2014 14:07:29 -0500, Paul Gilmartin wrote:
>
>>Are there separate pools of real storage for above the bar and below the bar?
>
>Pools? No. Pools are a software concept.
>
>Real storage with real addresses < 2 GiB are below the bar.
>Real storage with real addresses > 2 GiB are above the bar.
>
ITYM ">= 2 GiB"

But what do you call real storage with a real address = 3 GiB or
thereabouts?  I understand that for historic reasons, pertaining
only to z/OS, not other OSes, 2 GiB <= virtual address < 4GiB
is prohibited, and GETMAIN (STORAGE?) for even 64-bit
addressable storage will not return storage in that area.  But
why?  What harm would befall if it did?

>A GETMAIN request can specify whether the storage is to be backed by real 
>storage < 16 M, <2 G, or anywhere.
> 
Why should the application even care?  Doesn't virtual storage appear
the same regardless where it's physically backed?

-- gil

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