What about a driver program which OPENs a DD name then ATTACHes the actual 
"main" routine with the DCB=. This driver has an API such that a subtask can 
request the driver program, in its TCB, do a CLOSE / DEALLOCATE / ALLOCATE / 
OPEN of the DCB which it used in the ATTACH? Granted, this is likely very 
dangerous due to timing issues (or ENQ SMC). But does the IBM documentation 
explicitly say that the parent TCB cannot do this? "That which is not 
specifically forbidden, is allowed."

<quote>
,DCB=dcb addr
    Specifies the address of the data control block for the partitioned data 
set containing the entry name.

    Note: The DCB must be opened before the ATTACH macro is issued and must be 
the DCB used in the BLDL that built the 62-byte DE list entry. The DCB must 
remain open until the subtask becomes active, and it should not be closed 
immediately following the ATTACH.

    Note: DCB must reside in 24-bit addressable storage. 
</quote>

seems vague to me. Is the DCB actually used? Or the DEB pointed to by the DCB? 
The above says "should not be closed immediately". How long after the ATTACH? 
Or should it say only after the subtask terminates?

--
John McKown 
Systems Engineer IV
IT

Administrative Services Group

HealthMarkets(r)

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> -----Original Message-----
> From: IBM Mainframe Discussion List 
> [mailto:IBM-MAIN@bama.ua.edu] On Behalf Of Jim Mulder
> Sent: Friday, July 22, 2011 2:07 PM
> To: IBM-MAIN@bama.ua.edu
> Subject: Re: dynamic STEPLIB
> 
> IBM Mainframe Discussion List <IBM-MAIN@bama.ua.edu> wrote on 
> 07/22/2011 
> 08:46:56 AM:
> 
> > Not every product that runs under TSO/ISPF can use LIBDEFs 
> or ALTLIBs, 
> or
> > TASKLIBs.
> > 
> > I think there is a Share requirement out there (for ages I 
> think) for 
> IBM to
> > address this issue.  So far, there is still no dynamic 
> Steplib process.
> > 
> > I think the TSO-REXX group has had some discussions on this 
> topic as 
> well.
> 
>   The only supported mechanism in MVS for adding to the
> module library search order within as address space is an ATTACH with 
> a TASKLIB.  This is the only supported way to set TCBJLB.
> 
>   Any program which modifies TCBJLB in an existing TCB is
> wrong to do so.  I would recommend against having any such
> program installed on your system. 
> 
> Jim Mulder   z/OS System Test   IBM Corp.  Poughkeepsie,  NY
> 
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