Suggestion:  Add DD keyword SKIP.  Similar to DUMMY, but will continue
with the next concatenated DD statement.

On Tue, Feb 4, 2014 at 9:09 AM, Blaicher, Christopher Y.
<[email protected]> wrote:
> David,
>
> The use of DD DUMMY in a concatenation ends the processing of input data.  
> The following is from the JCL Reference Manual:
>
> Data sets concatenated to dummy data sets: The system treats data sets
> concatenated to a DUMMY data set as dummy data sets in that I/O operations are
> bypassed. However, the system performs disposition processing and allocates
> devices and storage for any concatenated data sets.
>
> So, in your example you only read the file once.  Without the DD DUMMY it 
> would read the file twice.
>
> Chris Blaicher
> Principal Software Engineer, Software Development
> Syncsort Incorporated
> 50 Tice Boulevard, Woodcliff Lake, NJ 07677
> P: 201-930-8260  |  M: 512-627-3803
> E: [email protected]
>
>
> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:[email protected]] On 
> Behalf Of Jousma, David
> Sent: Tuesday, February 04, 2014 8:45 AM
> To: [email protected]
> Subject: Re: Dummy dataset
>
> No, we have users sorting data with path names as input.  Just ran a test.  
> Single path input, concatenated, all work fine, unless they add a DD DUMMY 
> between them.  As a side note, DFSORT doesn't do a good job with dynamic 
> sortwk allocations with PATH input because it cannot accurately determine the 
> input filesize.   I had opened a ticket with IBM on this, and all I got was 
> "this is the way it is".   My only option was to tell my developers to 
> hardcode sorkwk datasets in their job.
>
> //DFSORT   EXEC PGM=SORT
> //SORTIN    DD PATHDISP=KEEP,
> //             PATHOPTS=ORDONLY,
> //             FILEDATA=TEXT,
> //             RECFM=VB,LRECL=255,BLKSIZE=25496,
> //             PATH='/etc/httpd1443.conf'
> //          DD DUMMY
> //          DD PATHDISP=KEEP,
> //             PATHOPTS=ORDONLY,
> //             FILEDATA=TEXT,
> //             RECFM=VB,LRECL=255,BLKSIZE=25496,
> //             PATH='/etc/httpd1443.conf'
>
> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:[email protected]] On 
> Behalf Of Paul Gilmartin
> Sent: Tuesday, February 04, 2014 8:37 AM
> To: [email protected]
> Subject: Re: Dummy dataset
>
> On Thu, 30 Jan 2014 20:18:05 +0000, Jousma, David wrote:
>
>>We have an exit for DFSORT that scans TIOT to see if someone concatenated a 
>>DUMMY dataset as input.  Here is what I believe to be the relevant snippet of 
>>code:
>>    ...
>>*                                 CHECK FOR DUMMY DD STATEMENT
>>*                                 NOTE: COULD ALSO BE DD *
>>DDCHK    CLC   TIOEFSRT,=AL3(0)   Q. REAL UCB ADDRESS ?
>>         BE    DDBAD              A. NO, BAD DD
>>    ...
>>
> How does this behave for DD PATH=...?  Is the UCB address nonzero for zFS 
> files?  Are you unwittingly prohibiting use of zFS in the SORTIN 
> concatenation?  That would be imprisoning your users in the twentieth century.
>
> Prohibiting "DD *" is also unduly harsh.
>
> A similar question applies to Shmuel's suggestion of DEVTYPE.
>
> The definitive test should be for DSNAME='NULLFILE'.
>
> -- gil
>
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-- 
Mike A Schwab, Springfield IL USA
Where do Forest Rangers go to get away from it all?

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