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What is DUMMY dataset

 
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krbabu

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Joined: 20 Feb 2004
Posts: 57

PostPosted: Thu Feb 26, 2004 3:00 pm    Post subject: What is DUMMY dataset
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hi all,

Can anybody explain about what is DUMMY data set and what is its use?
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sandip_datta

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Joined: 02 Dec 2003
Posts: 151
Location: Tokyo, Japan

PostPosted: Thu Feb 26, 2004 3:27 pm    Post subject:
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Hello Ravindra,

Dummy dataset is a welknown concept in CA-7.

Say there are partner systems from where you receive files and you want that when one particular file is reached in your system a particular job say JOB1 at your end will be triggered. In this case the partner system should send a dummy dataset A.JOB1 to your system after the original file and in your side JOB1 will have a dependency in that dummy dataset. This can be done in CA-7. When the dummy dataset reaches in your system the job will automatically started.

You can also check in CA-7 whether the dummy dataset has reached or not.
LCTLG,DSN=A.JOB1,LIST=ALL

I think others can give you a very good language from manual. Let's wait for that.

Regards,
Sandip.
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Johore

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Joined: 12 Sep 2003
Posts: 19

PostPosted: Thu Feb 26, 2004 6:05 pm    Post subject:
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Are you asking about the DD DUMMY we use in JCL icon_question.gif

If so then Dummy is used instead of DSN=dataset name to run the job for testing purposes , when we dont have actual data or the dataset with us. The Job will not abend with DATASET NOT FOUND.
Quote:
File is not present.
//ddname DD DUMMY,
// DCB=(LRECL=rec-len,BLKSIZE=blk-size,RECFM=rec-format)
Example:
//INFILE DD DUMMY,
// DCB=(LRECL=80,BLKSIZE=800,RECFM=FB)


This is purely used only in testing or Bypassing datasets for our test runs.
Hth
johor
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pr_ibm

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Joined: 04 May 2005
Posts: 9

PostPosted: Wed May 04, 2005 7:32 pm    Post subject:
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Yes you are correct Johor. If you dont know the file or some times there is a requirement like we dont want all the files in the job then if we omit any DD name we will get abend. So to avoid this situation we use DUMMY.


Thanks
PR...
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gnagakishore

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Joined: 26 Mar 2005
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Location: Hyderabad

PostPosted: Sat May 07, 2005 10:17 pm    Post subject:
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dummy parameter is used to test the execution of the program with out
being reading or writing into it.
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mmwife

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Joined: 30 May 2003
Posts: 1592

PostPosted: Sun May 08, 2005 10:37 pm    Post subject: Re: About DUMMY dataset
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This is to correct the misconception that DD DUMMY is only used in a test environment. It is used quite often in production situations where a given run of a pgm doesn't require ALL the O/Ps generated by the pgm.

To generate them wastes DA space and can also confuse the collection of generations in a GDG.
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vivek_mvs1

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Joined: 25 Apr 2006
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PostPosted: Tue Jun 06, 2006 4:47 pm    Post subject:
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Hi,

Dummy is used one of my application. It is used to Deload a dataset throuh IDCAMS utility

Code:
/REPRO4  EXEC PGM=IDCAMS,COND=(4,LT)               
//SYSPRINT DD  SYSOUT=*                             
//SYSOUT   DD  SYSOUT=*                             
//IN       DD  DUMMY                               
//OUT      DD  DISP=OLD,DSN=BRLV.SRBRDCF           
//SYSIN    DD  *                                   
   REPRO INFILE(IN) OUTFILE(OUT)    REUSE  REPLACE 
/*                                                 


This is a equalent of giving a empty dataset

Please give me your suggestions if i am wrong

Regards,
Vivek
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skkp2006

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Joined: 14 Jul 2006
Posts: 93
Location: Chennai,India

PostPosted: Tue Jul 18, 2006 11:43 am    Post subject: Re: About DUMMY dataset
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Dummy dataset can be used in multiple scenarios.But what DD Dummy actually does is that it ignores the input and the output parameters(like disp,space,vol).Correct me if i am wrong icon_smile.gif
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shreevamsi

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Joined: 23 Feb 2006
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Location: Hyderabad,India

PostPosted: Tue Jul 18, 2006 2:04 pm    Post subject: Re: About DUMMY dataset
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Hi,

DUMMY...some times usefull in case of Generic Programs.

The DD is Coded with a Dataset/Dummy based on the requirement.

For Example, a program generates a Monthly Report and Daily Reports.

When Monthly Job is Run, The dataset to create Daily Report is Coded as Dummy.
Similarly, for daily job, monthly report dataset is DUMMY.

note: In both the scenarios, the PGM is same, creating Daily and Monthly Reports.

But the Job output varies from the Run.

~Vamsi
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parikshit123

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Joined: 01 Jul 2005
Posts: 269
Location: India

PostPosted: Fri Jul 21, 2006 12:50 pm    Post subject: Re: About DUMMY dataset
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skkp2006 wrote:
Dummy dataset can be used in multiple scenarios.But what DD Dummy actually does is that it ignores the input and the output parameters(like disp,space,vol).Correct me if i am wrong icon_smile.gif


I wonder if DUMMY ignores the DD parameters.

Can anyone throw light on this?
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Holger

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Joined: 24 Oct 2006
Posts: 2

PostPosted: Tue Oct 24, 2006 3:01 pm    Post subject: Re: What is DUMMY dataset
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Hi all,

DUMMY has in above the same meaning as NULLFILE and is used to suppress unused files. If you use it, it handles files as non existing.

You can use it for example in IDCAMS with various input and output files.
You have 20 input and 20 output files, but you only want to use the 9th thru 13th input/output files without changing the sysin instructions (REPRO).
So you set inpu/output file 1 thru 8 and 14 thru 20 to DD DUMMY.
It works, try it.

If you use it in a concatenated DD statement, be careful, because it
identifies the EOF in the DD DUMMY, so it is the best way to place it
at the end of a DD instruction.

All parameters used after a DD DUMMY, are ignored, this is the difference between NULLFILE and DD DUMMY. NULLFILE recognizes applied parameters.

Greetings
Holger
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Holger

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Joined: 24 Oct 2006
Posts: 2

PostPosted: Tue Oct 24, 2006 3:39 pm    Post subject: Re: What is DUMMY dataset
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One additional information. If you want to create an eighty bytes lon dataset, you can use DUMMY as input file with DCB=LRECL=80 and create an output file from this file is created with this attributes.

Greetings
Holger
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