According to my OS/390 Collection March 1999 Version 2 Release 7.0:
RENT: MVS *protects your module's virtual storage so that your module
cannot be modified* - and REFR implies RENT.
See attached (this time without Unicode formatting <g>.)
Cheers, Chris Poncelet (retired sysprog consultant)
On 26/08/2021 04:54, Jim Mulder wrote:
> YDNRC. In general, the frame steal code has no knowledge
> that a frame contains a program, or that the program
> is REFR. The only exception to that is the PLPA and EPLPA
> virtual storage ranges, for which the frame steal code does
> steal without paging out, effectively treating everything in
> those ranges as conceptually REFR for stealing purposes,
> regardless of the load module attributes.
>
> Jim Mulder z/OS Diagnosis, Design, Development, Test IBM Corp.
> Poughkeepsie NY
>
> "IBM Mainframe Discussion List" <IBM-MAIN@LISTSERV.UA.EDU> wrote on
> 08/25/2021 09:10:04 PM:
>
>> From: "CM Poncelet" <ponce...@bcs.org.uk>
>> To: IBM-MAIN@LISTSERV.UA.EDU
>> Date: 08/25/2021 11:21 PM
>> Subject: Re: RENT binder option
>> Sent by: "IBM Mainframe Discussion List" <IBM-MAIN@LISTSERV.UA.EDU>
>>
>> IIRC The page(s) of an LMOD marked REFR can be stolen without having
>> first to back it up to cache, because it can be REFReshed from cache (or
>> DASD) and continue to execute as if its page(s) had not been stolen -
>> e.g. in the PLPA. If it modified itself, it would hit a S0C4-4. AFAIK A
>> backup/swap-out would be needed if it was marked RENT but not REFR.
>
>
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From my OS/390 Collection March 1999 Version 2 Release 7.0 (CD 1 of 9)
7.3.30 REUS: Reusability Options
The REUS option allows you to specify how a program may be reused. (Reusability
means that the same copy of a program module can be used by more than one task
either concurrently or one after another.)
Note that the value of the REUS option always overrides the reusability of any
included load modules or program objects.
The syntax of the REUS option is as follows:
+------------------------------------------------------------------------+
¦ ¦
¦ REUS={NONE|SERIAL|RENT|REFR} ¦
¦ ¦
+------------------------------------------------------------------------+
The reusability values are:
NONE
The module cannot be reused. A new copy must be brought into virtual
storage for each use. NONE is the default value.
SERIAL
The module is serially reusable. It can only be executed by one task at a
time; when one task has finished executing it another task may begin. A
serially reusable module may modify its own code, but when it is re-executed it
must initialize itself or restore any instructions or data that have been
altered.
RENT
The module is reenterable. It can be executed by more than one task at a
time. A task may begin executing it before a previous task has completed
execution. A reenterable module cannot modify its own code. (MVS *protects
your module's virtual storage so that your module cannot be modified*.)
Reenterable modules are also serially reusable.
REFR
The module is refreshable. *It can be replaced by a new copy during
execution without changing the sequence or results of processing. A
refreshable module cannot be modified during execution*.
A module can only be refreshable if all the control sections within it are
refreshable. The refreshable attribute is negated if any input modules are not
refreshable. *Refreshable modules are also reenterable and serially reusable*.
The refreshable attribute can be specified for any non-modifiable module.
Alternatively, you can code a REUS option as a single keyword without a value
(REUS, NOREUS, RENT, NORENT, REFR, NOREFR). For example:
--------------------------------------------------------------------------
//LKED EXEC PGM=IEWBLINK,PARM='RENT,...'
--------------------------------------------------------------------------
This alternative form is supported only for backward compatibility. The most
restrictive positive specification is used to set the reusability attribute.
For example, specifying REFR has the same effect as specifying REUS (REFR) and
the module is marked as refreshable, reenterable, and (serially) reusable.
If the PARM string contains both formats, the REUS(value) instance will
override any reusability options specified without values.
The binder only stores the attribute in the directory entry. It does not check
whether the module is actually reenterable or serially reusable. If the module
is incorrectly marked as reenterable or reusable, execution results are
unpredictable; for example, a protection exception might occur or the program
might use another task's data.
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