Don It turns out there is some amazing sophistry which can explain the grin on the non-existent Cheshire Cat!
The copper-bottomed line is that, indeed, all suboperands of DISP relate to the data set and, in that case where the DSNAME specifies a member, none of the suboperands of DISP relate to the member. That confusing paragraph which implied that a data set could exist already with DISP=NEW - or why was the existence or otherwise of the member pertinent - can be explained as follows: - Let us say the program wants to open and close the data set N times and at least the first time one or more records (blocks) are written. -- If DISP=OLD or DISP=SHR is specified and the data set (pds) exists already, this is fine. -- If DISP=NEW is specified and the data set didn't exist already, the first "open and close" will work, but the second open causes a failure since now the member exists. -- If DISP=MOD is specified and the data set didn't exist already, the first "open and close" will work, but the second open causes a failure since now the member exists. -- If DISP=MOD is specified and the data set existed already but the member didn't exist, the first "open and close" will work, but the second open causes a failure since now the member exists. -- If DISP=MOD is specified, the data set existed already and the member existed already, the first open causes a failure since the member exists. For convenience, here's that pesky paragraph again: <quote> When you specify DISP=MOD or DISP=NEW for a partitioned data set (PDS) or partitioned data set extended (PDSE), and you also specify a member name in the DSNAME parameter, the member name must not already exist. If the member name already exists, the system terminates the job. </quote> Charles Mills did hint at this earlier but I'm afraid I missed his point. Of course, why this should be a problem is not clear - or not to me anyhow - and when something like this isn't clear it behoves the developers to explain themselves - and sometimes they do, sometimes they don't! Chris Mason On Sun, 6 Mar 2011 09:49:03 -0500, Don Williams <donb...@gmail.com> wrote: >When I replied with my "simple" answer, I had not seen the part of thread >referring to product being written. Over the years, I have had to restore >many PDSes when a naïve user coded DISP=(MOD,DELETE). Sorry, I'm biased with >trying to make sure that most people view, in general, DISP as a dataset >level parameter. However, in this case the nuances of the DISP parameter are >important. > >Don > >-----Original Message----- >From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On Behalf >Of Chris Mason >Sent: Saturday, March 05, 2011 11:44 PM >To: IBM-MAIN@bama.ua.edu >Subject: Re: Difference between DISP=NEW and MOD for a PDS member? > >Don > >> The simple answer: > >This is not a topic for people who need "simple answers"! > >When I said > >>...> DISP=NEW/MOD insists that the member does not exist irrespective of >whether or not a partitioned data set exists > >obviously I was concentrating on the only on first suboperand of the DISP >operand. > >It seems we must take a different perspective according to whether we are >dealing with the first suboperand or the second and third suboperands - not >at >all "simple"! > >> The DISP parameter is for the data set/library and not members. > >Apparently not so in the case of the first suboperand. > >If a member name is specified, the first suboperand relates to the member >and >appears not to care about the data set. Otherwise why make a fuss about >whether a member exists or not in a data set that can't be there to contain >the member - which may or may not be there - if the data set is not supposed > >to exist - in the case of DISP=NEW anyhow. There's something of the >Cheshire Cat about this! > >Here, once again for your delectation, is the first paragraph of the >section "12.19.8 Disposition of Partitioned Data Sets (PDSs and PDSEs)" from > >the z/OS V1R12 MVS JCL Reference manual: > >http://publibz.boulder.ibm.com/cgi- >bin/bookmgr_OS390/BOOKS/IEA2B6A0/12.19.8 > ><quote> > >When you specify DISP=MOD or DISP=NEW for a partitioned data set (PDS) or >partitioned data set extended (PDSE), and you also specify a member name in >the DSNAME parameter, the member name must not already exist. If the >member name already exists, the system terminates the job. > ></quote> > >If you can explain this away, I'll accept your "simple" contention also >regarding >the first suboperand. > >> For example, DSN=MY.LIBRARY(MYMEM),DISP=(OLD,DELETE) deletes the >library and not just the member. > >Assuming you verified your example rather than just composing it in order to > >illustrate your point, it appears that the normal and abnormal termination >disposition suboperands do indeed apply to the data set irrespective of >whether or not a member name is specified. I checked the z/OS V1R12 MVS >JCL Reference manual to try to be sure and there is certainly no mention of >any variation based on whether or not a member name is specified so I guess >an actual test would have been superfluous. > >http://publibz.boulder.ibm.com/cgi- >bin/bookmgr_OS390/BOOKS/IEA2B6A0/12.19.2.2 >http://publibz.boulder.ibm.com/cgi- >bin/bookmgr_OS390/BOOKS/IEA2B6A0/12.19.2.3 > >Indeed, it's all getting a bit complex and the poor systems programmer who >tried to delete a member using the DISP second suboperand can be forgiven - >well by those who were not desperately relying on the partitioned data set, >that is![1] > >- > >A modification to my previous post with the diagrams: > >In the case of a DISP=NEW data set or dataset(member) - and DISP=MOD if >the entity has had no existence hitherto - it is an error not to write >something. This makes my "error or immediate EOF" simply "error". >An "immediate EOF" would be possible only if the data set - or a member I >guess - had deliberately been created - "written to" - with 0 records. >Alternatively I'll be happy to be corrected. > >- > >Chris Mason > >[1] This reminds me of an occasion when I keyed up a SCRATCH statement >that was supposed to be coded as > >SCRATCH VTOC,VOL=2314=MYVOLM,SYS > >After that traumatic event, I resolved always to use the order > >SCRATCH VTOC,SYS,VOL=2314=MYVOLM > >because it turns out you can't always be sure that where you intended to key > >a comma, a comma actually got keyed! > >I remember even better because it was New Year's Eve and the was someone >from north of the border in the overworked team. > > >On Sat, 5 Mar 2011 15:12:41 -0500, Don Williams <donb...@gmail.com> >wrote: > >>The simple answer: The DISP parameter is for the data set/library and not >>members. >> >>For example, DSN=MY.LIBRARY(MYMEM),DISP=(OLD,DELETE) deletes the >library and >>not just the member. >> >>-----Original Message----- >>From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On >Behalf >>Of Charles Mills >>Sent: Friday, March 04, 2011 3:03 PM >>To: IBM-MAIN@bama.ua.edu >>Subject: Difference between DISP=NEW and MOD for a PDS member? >> >>What is the difference between DISP=NEW and DISP=MOD for a PDS member >>(member name specified on the DD statement)? >> >>Both disallow duplicate member names. Are there any differences? What? >> >>Charles ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
