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Doubt in Variable record length

 
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Husna

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Joined: 02 Jun 2006
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PostPosted: Tue Jul 04, 2006 11:00 am    Post subject: Doubt in Variable record length
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Hi,

Could you please clarify the following concept?

For Fixedblock: DSN=(RECFM=FB,LRECL=80,BLKSIZE=800)

LRECL =80 and it takes multiples of it (80*10=800) for BLKSIZE

In the case of Variable:

DSN=(RECFM=VB,LRECL=84,BLKSIZE=840)

LRECL =80 (Plus 4 for Variable length record) and it takes multiples of it (84*10=840) for BLKSIZE

In LRECL we need to mention 80 or 84?

Will you please let me know answer for the same?
Awaiting your reply.
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prashantshinde

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Joined: 25 Nov 2005
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PostPosted: Tue Jul 04, 2006 11:09 am    Post subject: Re: Doubt in Variable record length
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You wrote :
DSN=(RECFM=VB,LRECL=84,BLKSIZE=840) ???

Firstly you should write 'DCB' instead of 'DSN' for defining DCB parameters.

The LRECL for Variable Block record format should be 80,as the 4 bytes for address and length of record are managed internally.
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Husna

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PostPosted: Tue Jul 04, 2006 11:26 am    Post subject:
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Prashant,

Thanks for the reply.

You wrote:

The LRECL for Variable Block record format should be 80,as the 4 bytes for address and length of record are managed internally.


Could you please let me know about BLKSIZE?
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kondakonda

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PostPosted: Tue Jul 04, 2006 12:07 pm    Post subject: Re: Doubt in Variable record length
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Hi,

For this example,
DCB=(LRECL=80,RECFM=VB,BLKSIZE=84)
Internally each record is stored with maximum length of 84 (4 bytes for record length)
as the BLKSIZE=84 there wont be any unused space

For this example,
DCB=(LRECL=80,RECFM=VB,BLKSIZE=88)
there will be 4 bytes of unused space for every block.

We can define like anything but should always prefer to avoid unused space.


Thanks.
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prashantshinde

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PostPosted: Tue Jul 04, 2006 1:09 pm    Post subject:
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Husna wrote:


Could you please let me know about BLKSIZE?


[red]BLKSIZE[/red] :

In the context of JCL BLKSIZE is same as u have written ..like multiple of LRECL . You would find it more iteresting with COBOL and VSAM

See the attachment
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Frank Yaeger

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PostPosted: Tue Jul 04, 2006 8:20 pm    Post subject:
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Quote:
LRECL =80 (Plus 4 for Variable length record) and it takes multiples of it (84*10=840) for BLKSIZE


For VB, the BLKSIZE can be any value greater than or equal to LRECL+4. The BLKSIZE does NOT have to be a multiple of LRECL+4. So for an LRECL of 80, the BLKSIZE can be 84 or greater. Usually, the system determined BLKSIZE (SDB) is a good choice (approx. half-track for DASD = 27998 on a 3390 for LRECL=80). A small BLKSIZE like 84 is not an efficient choice.
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raviprasath_kp
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PostPosted: Sun Oct 08, 2006 8:54 pm    Post subject:
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any one can advice me what is the main diffence between FB VB
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Frank Yaeger

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PostPosted: Sun Oct 08, 2006 11:40 pm    Post subject:
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With F, all of the records are the same length as defined by the LRECL.

With V, records can be different lengths up to the maximum as defined by the LRECL.

F or V indicates that the records are unblocked. FB or VB indicates that the records are blocked.
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