In
<ofad40972b.2f224bfe-on85257b21.005f5b59-85257b21.00638...@us.ibm.com>,
on 03/01/2013
at 01:07 PM, Jim Mulder <d10j...@us.ibm.com> said:
>My understanding from folklore is that the REFR attribute predates
>MVS, and its purpose was to designate modules for which a new copy
>of the module could be safely loaded (refreshing) after a storage
>related machine check.
Correct.
>So if you are asking why the designers at that time did not choose
>to also use the REFR attribute for write protection purposes, I
>can only speculate. Since that predated address spaces, the only
>choice for write protection would be using storage key 0. I don't
>know whether or not there was any means at that time for
>providing key 0 storage within a region.
There was, e.g., subpool 252.
>But to allow the code to be fetched while executing in the
>region's key, key 0 storage would have to be non-fetch protected.
As I recall, none of the subpools for load modules were fetch
protected. In fact, I don't recall any support for fetch protect in
OS/360, although IBM might have added it for RSS.
--
Shmuel (Seymour J.) Metz, SysProg and JOAT
Atid/2 <http://patriot.net/~shmuel>
We don't care. We don't have to care, we're Congress.
(S877: The Shut up and Eat Your spam act of 2003)
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