Coding RECFM=F over RECFM=FB

What is the advantage of coding RECFM=F over RECFM=FB why not F.

Questions by karthikmainframes1

Showing Answers 1 - 9 of 9 Answers

If you code with RECGM=F , 

Disadvantages:

            1) The read and write operations will be slow.

            2) It requires more buffer space also.

Advantages:

           1) The predecessor job can not see the blocked data.


Please correct me if i am wrong.

Thanks,
Lavanya T

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dhs01

  • Apr 15th, 2009
 

I could be wrong but years ago, F meant unblocked. Just tried it, F by itself still means unblocked. (ie LRECL=BLKSIZE)

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The main difference is,
If we use RECFM=F then, if the dataset is having the LRECL as 80 then the BLK size will also be 80.
If we use RECFM=FB then, if the dataset LRECL is 80 then the BLK size we can take as multiples of 80 eg:80,800,8000...and so on

Please correct me if i am wrong
Thanks & regards
Haritha

dhs01

  • Sep 16th, 2009
 

The other 2 answers are correct. This one is questionable.

If you code with RECGM F
Disadvantages:
1) The read and write operations will be slow. 

Sequentially reading the entire file could be slower since an i/o would give less of the file. (ie more i/o although there are ways around this via chaining ccws, etc.) Each individual i/o would actually be a bit faster since you would be using BSAM which I would bet will out perform QSAM on an individual i/o also the amount of data being transfered per read would be smaller.

2) It requires more buffer space also.
Not really true. Buffers would be smaller.

Advantages:
1) The predecessor job can not see the blocked data.
The data is not blocked - there is no blocked data

Please correct me if I am wrong.

Thanks
Lavanya T


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2chumma2

  • Dec 7th, 2009
 

In PS and PDS datasets  the record format "F" is fixed which means all the records in the datasets have same length. 


Blocking means grouping of records into blocks before they are written in to volume. This blocking reduces the IBG (inter block gaps ).
Blocking conserves storage space on a volume by
reducing the number of inter-block gaps in the data set, and increases processing efficiency
by reducing the number of I/O operations required to process the data set.
Blocking can be done for both Fixed Length records (RECFM=FB) and Variable length
records (RECFM=VB)

F   REC1 IBG REC2 IBG
FB REC1 REC2 REC3 REC4 IBG

Since a block consists of one or more records, block size is usually multiple of record size.

If we give RECFM=F then it indicates the file is a flat file.
If we give RECFM=FB then it indicates the file is for reporting purpose. this means it reserves the First position of the record for the report format.

Please correct me if I am wrong.. 

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ananta2010

  • Jun 11th, 2010
 

RECFM=F record formate = F means fixed in whcih block and records are of same size.

RECFM=FB fixed block in this several logical records are combined into one physical block.

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guraddiv

  • Jan 25th, 2011
 

RECFM=F means each record will be stored in each block, where as in FB group of records will be stored in one block.


Please correct me if i am wrong.

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