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CKD and FBA

 
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praveensinha
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PostPosted: Tue Apr 20, 2010 2:47 pm    Post subject: CKD and FBA
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What are FBA (fixed block architecture) N CKD devices(count key data )
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Robert Sample

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PostPosted: Tue Apr 20, 2010 2:54 pm    Post subject:
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Google is your friend. Googling fba ckd returns 149,000 hits and some of them on the first page will answer your questions.
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vasanthz

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PostPosted: Tue Apr 20, 2010 2:58 pm    Post subject:
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FBA -
'A' denotes that the data set contains the ASA print control parameters to communicate with the printer.

If u provide a FB dataset in SYSPRINT of a job, u can note that the dataset would be converted from FB to FBA.
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enrico-sorichetti

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PostPosted: Tue Apr 20, 2010 3:01 pm    Post subject: Reply to: CKD and FBA
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the TS has already pointed out that he wants to know about the differences in dasd architectures

FBA Fixed Block Architecture
CKD Count Key Data

not about the DCB attributes of a dataset
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praveensinha
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PostPosted: Tue Apr 20, 2010 3:36 pm    Post subject:
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I have searched earlier ,bfore posting my question .... I am not able to understand the diff between CK n FBA..

It is some thing like

FBA

FBA devices appear as linear address spaces of 512-byte blocks. The blocks are consecutively numbered from 0 to n, where n is the highest block number on the volume. z/VM groups eight consecutive blocks to form a z/VM page and this page must begin on a 4 KB boundary. z/VM then views the volume as a collection of pages numbered from 0 to (n-7)/8. For example, blocks 0-7 make up page 0. There is no concept of cylinder boundaries in this structure.


CKD

z/VM views CKD devices by their geometric characteristics (such as number of cylinders). Each cylinder has a fixed page capacity, meaning that a fixed number of 4 KB records fit on a cylinder. This number varies for each CKD DASD type. z/VM references its data by a cylinder number and a page number on that cylinder. For z/VM space you must format and allocate pages in groups of cylinders.
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Robert Sample

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PostPosted: Tue Apr 20, 2010 4:58 pm    Post subject:
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If you Google gx26-4577 you can find the 3390 DASD Reference Summary. Page 10 of this summary has a detailed explanation of where the count, key, and data values come from.

However, your last post summarizes the differences nicely:

FBA -- "no concept of cylinder boundaries"
CKD -- "allocates ... in groups of cylinders" (or tracks)
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