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why do we use VSAM files instead of ordiary files

 
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princeaggarwal

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PostPosted: Thu Apr 05, 2007 1:46 pm    Post subject: why do we use VSAM files instead of ordiary files
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VSAM files are for reason being used in Mainframe.
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vkphani

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PostPosted: Thu Apr 05, 2007 1:52 pm    Post subject:
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1. You can have primary key in case of VSAM files.
2. You can not add or delete records in an ESDS file.
3. Faster access to data.
4. CICS supports only VSAM files.

and many more.
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vkphani

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PostPosted: Thu Apr 05, 2007 1:53 pm    Post subject:
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5. You can directly go to a particular record in case of RRDS file.
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expat

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PostPosted: Thu Apr 05, 2007 1:57 pm    Post subject:
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Quote:
2. You can not add or delete records in an ESDS file.

Are you sure about this ?
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vkphani

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PostPosted: Thu Apr 05, 2007 2:03 pm    Post subject:
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Quote:
Are you sure about this ?


Yes
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expat

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PostPosted: Thu Apr 05, 2007 2:03 pm    Post subject:
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Quote:

1. You can have primary key in case of VSAM files.
2. You can not add or delete records in an ESDS file.
3. Faster access to data.
4. CICS supports only VSAM files.


Point 1 - you can also have one or more alternate index(es) to acces the data via fields which are not the key of the base cluster.

Point 2 - In addition to the point raised in my previous post, ESDS can also be accessed via alternate index(es)

Point 3 - probably not since the introduction in RAID DASD technology.
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