That information is related to one of my systems programmer interview questions.

Mark Jacobs

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On Saturday, August 24th, 2024 at 8:32 PM, Seymour J Metz <[email protected]> 
wrote:

> Even with REFPROT=NO, programs from an authorized concatenation an marked 
> RENT go into key 0 storage.
> 
> --
> Shmuel (Seymour J.) Metz
> http://mason.gmu.edu/~smetz3
> עַם יִשְׂרָאֵל חַי
> נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר
> 
> 
> 
> ________________________________________
> From: IBM Mainframe Discussion List [email protected] on behalf of 
> Lennie Bradshaw [email protected]
> 
> Sent: Saturday, August 24, 2024 9:28 AM
> To: [email protected]
> Subject: Re: Non-reentrant program not allowed (where?); Advantages of 
> reentrant programs?
> 
> Clearly my statements below lack the degree of accuracy that is needed. 
> Apologies.
> 
> As others have stated the option is REFRPROT which refers to refreshable 
> modules rather than reentrant modules.
> Also it appears that the default has not changed. So refreshable modules are 
> loaded into non-store protected subpools by default, unless REFRPROT is 
> specified.
> 
> When it is specified, (taken from z/OS 3.1 MVS Initialization and Tuning 
> Reference SA23-1380-60),
> 
> "Note that the specification of REFRPROT will cause modules link-edited with 
> the REFR attribute to be
> placed into key0, non-fetch protected, page-protected storage, regardless of 
> their APF authorization."
> 
> Lennie
> 
> -----Original Message-----
> From: IBM Mainframe Discussion List [email protected] On Behalf Of 
> Lennie Bradshaw
> 
> Sent: 23 August 2024 18:11
> To: [email protected]
> Subject: Re: Non-reentrant program not allowed (where?); Advantages of 
> reentrant programs?
> 
> In addition to what others have said, these days reentrant programs are 
> usually loaded into store-protected subpools, even if they are not APF 
> authorised. This protects the program from being modified by anyone else 
> operating in the same address space, either accidentally or deliberately.
> As this was not always the case, and for compatibility purposes, it can be 
> disabled for non-authorised programs, I believe.
> 
> Lennie
> 
> -----Original Message-----
> From: IBM Mainframe Discussion List [email protected] On Behalf Of 
> Richard Zierdt
> 
> Sent: 23 August 2024 17:20
> To: [email protected]
> Subject: Non-reentrant program not allowed (where?); Advantages of reentrant 
> programs?
> 
> Some assembly textbook authors advise always writing reentrant code "because 
> you never know if your program will be" [placed in some library / system 
> space].
> The question is: where (e.g. what libraries) must programs be reentrant to be 
> "allowed in" ?
> Besides specific libraries (if any), are there other advantages to reentrant 
> code ?
> Thanks --
> Richard Zierdt
> 
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