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BDAM vs sequential dataset

 
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Chinnadu

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Joined: 05 Mar 2009
Posts: 42
Location: Hyderabad

PostPosted: Sat Sep 12, 2009 1:18 am    Post subject: BDAM vs sequential dataset
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Can anyone tell me what is the difference between sequntial data set and a BDAM dataset.
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dick scherrer

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PostPosted: Sat Sep 12, 2009 1:28 am    Post subject:
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Hello,

BDAM is used for direct access rather than sequential access.

The millionth record in a 5million record file can be read in one read rather than reading all of the records before it.
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Terry Heinze

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Joined: 14 Jul 2008
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Location: Richfield, MN, USA

PostPosted: Sat Sep 12, 2009 2:30 am    Post subject:
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Also, BDAM is no longer supported by COBOL. It's function, for the most part, has been replaced by RRDS VSAM files. Some vendors still use it. I think Panvalet files are BDAM. Also, I think IAM files, although simulating VSAM, are actually BDAM files.
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dick scherrer

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PostPosted: Sat Sep 12, 2009 3:02 am    Post subject:
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Hello,

The biggest use of BDAM that i've seen is in various database products.
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Chinnadu

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PostPosted: Tue Sep 15, 2009 8:30 am    Post subject: Reply to: BDAM vs sequential dataset
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Hi All,

Thank you very much for your clarifications, I have one more doubt.

What is the difference between BDAM and VSAM , functionality of both looks similar to me. Is there any difference.Please clarify.
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Terry Heinze

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PostPosted: Tue Sep 15, 2009 8:41 am    Post subject:
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Virtual Storage Access Method files can be Entry Sequenced Data Sets (similar to BSAM or QSAM), Relative Record Data Sets, Key Sequenced Data Sets (similar to the old ISAM files), or Linear Data Sets. Basic Direct Access Method files are most like RRDS. Google is your friend.
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Anuj Dhawan

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PostPosted: Tue Sep 15, 2009 5:16 pm    Post subject:
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Optionally, BDAM uses hardware keys. Hardware keys are less efficient than the optional software keys in virtual sequential access method (VSAM).
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dick scherrer

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PostPosted: Tue Sep 15, 2009 9:14 pm    Post subject:
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Hi Anuj,

Quote:
Hardware keys are less efficient than the optional software keys in virtual sequential access method (VSAM).
Maybe (i've not heard that particular thought before), but bdam (in every case that i've worked with) far outperforms vsam . . .
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Terry Heinze

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PostPosted: Tue Sep 15, 2009 10:01 pm    Post subject:
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Quote:
...bdam (in every case that i've worked with) far outperforms vsam . . .
When I worked at a shop that converted from OS/VS COBOL to COBOL II, and therefore BDAM to RRDS VSAM, the BDAM files that some folks were used to had to be "pried from their cold, dead hands". icon_lol.gif
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