The whole disk is NOT in your virtual storage; The track window IS (IIRC).

Cheers, Martin

Sent from my iPad

> On 19 May 2016, at 21:45, Tony Harminc <[email protected]> wrote:
>
>> On 19 May 2016 at 01:44, Martin Packer <[email protected]> wrote:
>> It's sort of come back to me:
>>
>> A small track size limits the virtual storage window (probably usually
>> below the line in 1989 when I looked at this). Or it might've been
>> cylinder. But I think it was track.
>>
>> I'm wondering if anyone else remembers something like this.
>
> I'm not sure I get the "virtual storage window" idea. VIO emulates an
> entire disk drive in virtual storage. So where is there a window? The
> whole disk has to be in virtual storage at once. Well, I suppose there
> could be logic to not allocate Virtual until used, but that would
> surely better be left to VSM's and RSM's expertise at managaing their
> respective kinds of storage.
>
> Now maybe VIO was changed much later (surely there wasn't expanded
> storage in 1989...?) to use or perhaps favour expanded storage, in
> which case a window model could make some sense. But only if VIO was
> directly dealing with expanded storage rather than just requesting
> that RSM use it to back virtual storage used to hold the VIO disk
> data.
>
> Tony H.
>
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