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Diff b/w Sequential file and ESDS file

 
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bhgh
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PostPosted: Thu May 18, 2006 1:35 pm    Post subject: Diff b/w Sequential file and ESDS file
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Hi,
Can u give me answer for my question.

difference between sequential file and ESDS file.




thanks in advance

Rgds
kala
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sachina2z

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PostPosted: Thu May 18, 2006 2:29 pm    Post subject:
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sequential file is a normal dataset.
ESDS is a VSAM dataset, contains 2/3 supporting files for storing ur data.
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abhishekraghav

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PostPosted: Thu May 25, 2006 1:13 pm    Post subject:
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In addition to to Sachina2Z...

ESDS has control information....while sequential file does not.

ESDS can have alternative index and can be accessed through it.
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philipraju
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PostPosted: Thu May 25, 2006 1:45 pm    Post subject: In addition
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Sequential file (Qsam) can be created on tape while vasm files didn't on tape
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gskulkarni

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PostPosted: Thu May 25, 2006 1:48 pm    Post subject:
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sachina2z wrote:
sequential file is a normal dataset.


I believe all datasets are more or less 'normal' dataset only. Sometimes I have observed people who are not so 'normal' who access those datasets icon_smile.gif

ESDS and Sequential non-vsam dataset.
I assume you are pretty clar about what a sequential dataset is.

1. ESDS is a type of VSAM dataset which essentially operates similar to sequential dataset.
2. Any record written to ESDS is written at teh end of the file, much same as seq. dataset.
3. Direct access to any record is possible using Relative Byte address of the record. Sequential files do not have this feature.
4. Allocation of ESDS is similar to that of KSDS i.e. using IDCAMS utility using define cluster commands. Seq files can be allocated using DISP=NEW,CATLG,DELETE and space parameters.
5. A record in ESDS can be rewritten using direct access method. Whereas, in seq. datasets it is not possible.
6. Deletion of ESDS is done with IDCAMS DELETE . But seq. files can be deleted even using IEFBR14 utility with DISP=(NOD,DELETE,DELETE).

some of the above differences are purely from programmer's point of view. There are many diff as such because storage type is VSAM for ESDS whereas sequential datasets are non-vsam. I have tried to explain as much as possible.
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sundaresanjs

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PostPosted: Sat Jun 17, 2006 1:49 pm    Post subject:
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hi abhishekraghav,

ESDS file cannot have Alternate index,
alternate index is an extreme property of KSDS file only.


regards,
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