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Append to file, but also remove old records when full?

 
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tander3

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Joined: 21 Jan 2016
Posts: 2
Location: USA

PostPosted: Mon Jan 25, 2016 8:05 pm    Post subject: Append to file, but also remove old records when full?
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I have a JCL that triggers SAS code to compare files and record certain records.

New records append to the same file when the job runs. When the file is full the job abends.

Is there a way for the oldest records to drop from the file when new records append?

The file would have a fixed size, but never grow larger. I could change the SAS Code to help out with this, but I wonder if there a JCL only solution? That might be simpler.

Here is the JCL DD statement:

Code:

//RECORDS   DD DSN=FILE.NAME.RECORDS,               
//                  DISP=(MOD,CATLG),                         
//                  DCB=(RECFM=FB,LRECL=500,BLKSIZE=0),       
//                  AVGREC=M,SPACE=(500,(1,1),RLSE),UNIT=DISK


Thank you for reading my post !!
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Robert Sample

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Joined: 06 Jun 2008
Posts: 7913
Location: Bellevue, IA

PostPosted: Mon Jan 25, 2016 8:53 pm    Post subject: Reply to: Append to file, but also remove old records when full?
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Quote:
I could change the SAS Code to help out with this, but I wonder if there a JCL only solution?
First, JCL does nothing but allocate resources and execute programs. Hence you will NOT be able to find a JCL-only solution; you will have to use a program of some sort to do this.

Second, the system doesn't know how old a given record is -- the system tracks a data set as far as create date and last referenced date, but that's as far as it goes. So you'll need to write a program in the language of your choice to identify the oldest records and remove them from the data set. Note that removing them is easy if the data set is a VSAM KSDS but may be time-consuming if the data set is sequential since you'll probably need to copy it to an output data set omitting the old records from the write to the output data set.
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tander3

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Joined: 21 Jan 2016
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Location: USA

PostPosted: Mon Jan 25, 2016 10:03 pm    Post subject: Reply to: Append to file, but also remove old records when full?
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Ok - guess it's back into the SAS code then. - Thanks.
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Garry Carroll

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Joined: 08 May 2006
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Location: Dublin, Ireland / Edinburgh, Scotland

PostPosted: Tue Jan 26, 2016 1:51 pm    Post subject:
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Quote:
Is there a way for the oldest records to drop from the file when new records append?


..and what determines what's "oldest"? If you have a datestamp in the records, you could perhaps use a DFSORT/SYNCSORT step to drop the 'oldest' records before you current step appends more records?

Garry.
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