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sandhyaimmadi
New User
Joined: 18 Aug 2008
Posts: 50
Location: Bangalore
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Hi,
We have one sequential file.
We are not sure of how many thousands or millions of records it has.
If I have to process last 200 records.What needs to be done.
Please suggest.
Thanks. |
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Escapa
Senior Member
Joined: 16 Feb 2007
Posts: 1399
Location: IL, USA
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What I would suggest is..
Provide this file to Utility like DFSORT get only last 200 records in other file
provide that file to your cobol program for processing...
I am very sure that this is not business requirement and is homework or something you want to tryout....
There is also possible solution in cobol by reading file only once but as I said I would prefer earlier one... |
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sandhyaimmadi
New User
Joined: 18 Aug 2008
Posts: 50
Location: Bangalore
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| How to get last 200 records using DFSORT? |
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Pravesh
New User
Joined: 30 Jul 2009
Posts: 32
Location: Gurgaon
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If you have FileAid tool then you can copy 200 records from last and feed the same into your program.
other methos is using DFSORT you can add SEQ no to your file using INREC . You can have details at
www.ibmmainframes.com/about14136.html
then use sort card like
| Code: |
//SYSIN DD *
SORT FIELDS=COPY,
SKIPREC=X
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where X = Total record - 200
Thanks,
Pravesh |
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Escapa
Senior Member
Joined: 16 Feb 2007
Posts: 1399
Location: IL, USA
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| Quote: |
| How to get last 200 records using DFSORT? |
Here is DFSORT\ICETOOL step to give last 200 records from the file...
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//S1 EXEC PGM=ICETOOL
//SYSOUT DD SYSOUT=*
//DFSMSG DD SYSOUT=*
//TOOLMSG DD SYSOUT=*
//IN DD DSN=YOUR INPUT HERE
//OUT DD DSN=YOUR OUTPUT HERE
//TOOLIN DD *
SUBSET FROM(IN) TO(OUT) KEEP INPUT LAST(200)
/*
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sandhyaimmadi
New User
Joined: 18 Aug 2008
Posts: 50
Location: Bangalore
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Hi Pravesh,
How can we know the last seqnumber that is generated?
We should know this inorder to access last 200 records.
Thanks,
Sandhya. |
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Pravesh
New User
Joined: 30 Jul 2009
Posts: 32
Location: Gurgaon
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Hi Sandhya
FYI whenever we execute DFSORT using any input file, we have information like how many record processed in ouput msgs.
hope it will help you.
Thanks,
Pravesh |
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sandhyaimmadi
New User
Joined: 18 Aug 2008
Posts: 50
Location: Bangalore
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Thanks Pravesh,
I will try it out.
Right now, I have tried using ICETOOL which Escapa has given.
It is working. |
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mmwife
Super Moderator
Joined: 30 May 2003
Posts: 1592
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If you can use FileAid, use the following. It'sa lot faster. It reads the file backward.
| Code: |
//COPYKEY EXEC PGM=FILEAID
//DD01 DD DSN=YOUR.input.FILE
//DD01O DD DSN=file.contains.high.key
//SYSIN DD *
$$DD01 COPYBACK OUT=2000
/*
//*
//NEXT EXEC PGM=....
//HIGHKEY DD DSN=file.contains.high.key
//etc.... |
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006
Posts: 6248
Location: Mumbai, India
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| sandhyaimmadi wrote: |
We have one sequential file.
We are not sure of how many thousands or millions of records it has.
If I have to process last 200 records.What needs to be done. |
Millions - that's attractive. Is the file on tape? If yes, look at REVERSE verb in COBOL Manual. |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006
Posts: 19243
Location: Inside the Matrix
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Hello,
Many files that run into millions of records on "tape" are also multi-volume - which won't work with REVERSE. . . |
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enrico-sorichetti
Superior Member
Joined: 14 Mar 2007
Posts: 10886
Location: italy
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| Quote: |
| If I have to process last 200 records.What needs to be done. |
the safest thing ... fire the idiot who set the stupid requirement  |
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Ronald Burr
Active User
Joined: 22 Oct 2009
Posts: 293
Location: U.S.A.
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| dick scherrer wrote: |
Hello,
Many files that run into millions of records on "tape" are also multi-volume - which won't work with REVERSE. . . |
REVERSE "might" work if you specify DCB=OPTCD=B and VOL=SER=xxxxxx (where xxxxxx is the last volume serial number of the set ). Of course, that "assumes" that there will be 200 records on the last volser. If not, then the REVERSE technique with OPTCD=B will not work.
DCB=OPTCD=B requests the O/S to ignore the fact that the first reel of input is NOT the first reel of the dataset, and to also ignore the fact that the last specified reel may contain an EOV but not an EOF.
Note: a caution: DCB=OPTCD=B will not work if any OPTCD's were coded in the program source. |
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superk
Global Moderator
Joined: 26 Apr 2004
Posts: 4652
Location: Raleigh, NC, USA
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| I though you COBOL guys long ago stated on this forum that REVERSE had not been supported for quite some time. Did I mis-interpret this statement? |
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Robert Sample
Global Moderator
Joined: 06 Jun 2008
Posts: 8700
Location: Dubuque, Iowa, USA
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From the COBOL Language Reference manual:
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REVERSED
Valid only for sequential single-reel files. REVERSED is not valid for VSAM files.
If the concept of reels has no meaning for the storage medium (for example, a direct access device), the REVERSED and NO REWIND phrases do not apply.
NO REWIND
Valid only for sequential single-reel files. It is not valid for VSAM files. |
OPEN REVERSED is obsolete according to the COBOL standards committee. The option has not been made obsolete by IBM in its COBOL (so far). |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006
Posts: 19243
Location: Inside the Matrix
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Hi Kevin,
From the Enterprise Language Reference:
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REVERSED
Valid only for sequential single-reel files. REVERSED is not valid for VSAM files.
If the concept of reels has no meaning for the storage medium (for example, a direct access device), the REVERSED and NO REWIND phrases do not apply. |
Due to sheer volume, i've not used this in years. . . Of course, i also don't have a need to read the last few records of a many million record dataset. . . |
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Kjeld
Active User
Joined: 15 Dec 2009
Posts: 365
Location: Denmark
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Making a subset of the last 200 records with ICETOOL seems to work, the operation can be automated, which most of the REVERSE reading JCL techniques can't, at least not in all cases.
If the original dataset resided on tape, the subset can supposedly be written to DASD storage, speeding up the processing.
If the requirement for last 200 records are not fixed, the limit should be expressed in terms of some identification key in the data. I assume the sequence of the data in the original dataset is known. |
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Anuj Dhawan
Superior Member
Joined: 22 Apr 2006
Posts: 6248
Location: Mumbai, India
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To be very honest, this thread does really sound like a requirement to be implemented in production, is it a real requirement - I'd question.
On ther other hand, if the thread does not qualify for the question in above two lines, one should be better off by using ICETOOL or File-Aid options of doing it. I ran into such things copule of times and I used the file-aid to do that BUT then that was to do with "on the fly analysis" for some production-bug. |
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PeterHolland
Global Moderator
Joined: 27 Oct 2009
Posts: 2481
Location: Netherlands, Amstelveen
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I always read my hebrew papers/books backwards.
The strange thing is hebrew movies never start at the end. |
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Kjeld
Active User
Joined: 15 Dec 2009
Posts: 365
Location: Denmark
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| PeterHolland wrote: |
I always read my hebrew papers/books backwards.
The strange thing is hebrew movies never start at the end. |
But the dialogue is spoken backwards?  |
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PeterHolland
Global Moderator
Joined: 27 Oct 2009
Posts: 2481
Location: Netherlands, Amstelveen
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Not yet Kjeld.  |
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Kjeld
Active User
Joined: 15 Dec 2009
Posts: 365
Location: Denmark
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| Nah, I wouldn't be able to tell anyway |
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