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Difference between Flat Files and VSAM files

 
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sangeetha

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Joined: 06 May 2005
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PostPosted: Tue May 17, 2005 2:21 pm    Post subject: Difference between Flat Files and VSAM files
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why are flat files called so, what makes them different from vsam files?
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priyesh.agrawal

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Joined: 28 Mar 2005
Posts: 1452
Location: Chicago, IL

PostPosted: Tue May 17, 2005 2:49 pm    Post subject: Re: flat files
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Quote:
why are flat files called so,


Interesting question...sorry don't know the answer.

Quote:
what makes them different from vsam files?


VSAM Files need to have an index value in it.....there is no such constraints with Flat Files.......

Regards,

Priyesh.
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vasanthanc

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Joined: 01 Apr 2005
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PostPosted: Thu May 19, 2005 11:24 am    Post subject:
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flat files are called so because they are simple files which stores text, will not have any indexes or keys. Only sequential access is possible. It gives a flat llok to file and hence its called as flat files
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kanak

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Joined: 12 Mar 2005
Posts: 252
Location: India

PostPosted: Thu May 19, 2005 7:52 pm    Post subject:
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the organization of VSAM file is different than flat file. The way VSAM file is defined, is it need cluster which will consists of index and data area and that is mandatory.Where as for flat file index is not mandatory.
Flat file which are acces using index is just to make acces faster nothign else, but for VSAM fiel u always need an index.
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brain_s390

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Location: Mumbai

PostPosted: Sat May 21, 2005 1:43 pm    Post subject: Re: what is the difference between Flat Files and VSAM files
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Vsam is IBM's virtual storage access method.It provides sequential
indexed relative record dataset.VSAM increases the disk space requirements of systems. This is because VSAM offers certain
capabilities like partial self-reorganization to make things more efficient in data sets that can be
modified.
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superk

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Joined: 26 Apr 2004
Posts: 4648
Location: Raleigh, NC, USA

PostPosted: Tue May 24, 2005 2:20 am    Post subject: Re: what is the difference between Flat Files and VSAM files
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sangeetha wrote:
why are flat files called so, what makes them different from vsam files?

I don't know why they're called "flat files" either. I've heard of programmers referring to ASCII text files as "flat files", but I never heard of anyone referring to mainframe datasets by that term until I started to participate in this and other forums. It seems to me that usually only an applications programmer will refer to a dataset as a "flat file", whereas most of the rest of the IT world will call it a "Physical Sequential" or "QSAM" dataset.
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GAFUR

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Joined: 19 May 2005
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PostPosted: Tue May 24, 2005 6:16 pm    Post subject:
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HI

In VSAM files records are stored in control intervals where as in FLAT files records are stored in blocks.

FLAT files are sequential read . VSAM files can sequential and random read.

In VSAM acess is fast because of organization of records.

In FLAT files you can delete the record logicaly where as in VSAM physical delete is possible.
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