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CICS - sequential vs vsam question

 
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nani556
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PostPosted: Fri Jul 23, 2010 10:32 am    Post subject: CICS - sequential vs vsam question
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Hi,
I have a question that why we will not use flat files in cics.why we use VSAM files in CICS?

Pease help me.
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dick scherrer

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PostPosted: Fri Jul 23, 2010 7:26 pm    Post subject:
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Hello,

Is there some reason you replied to a completely unrelated topic?
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dick scherrer

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PostPosted: Fri Jul 23, 2010 7:29 pm    Post subject:
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Hello,

One reason is that sequential files imply "single user" - CICS is multiple users. QSAM files are a poor use of resources in a CICS environment.

VSAM files are to support multiple users.
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Ajay Baghel

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PostPosted: Fri Jul 23, 2010 8:32 pm    Post subject:
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Hi Dick,

Is that because of STRNO which is allowed for VSAM in FCT ?

Thanks
Ajay
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Robert Sample

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PostPosted: Fri Jul 23, 2010 8:43 pm    Post subject:
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From the CICS Programming Guide:
Quote:
3.2.7 Efficient sequential data set access

CICS provides a number of different sequential processing options. Temporary storage and intrapartition transient data queues (already discussed in "Temporary storage" in topic 3.1.6.6 and in "Intrapartition transient data" in topic 3.1.6.7) are the most efficient to use, but they must be created and processed entirely within CICS.

Extrapartition transient data is the CICS way of handling standard sequential (QSAM/BSAM) data sets. It is the least efficient of the three forms of sequential support listed, because CICS has to issue operating system waits to process the data sets, as it does when handling BDAM. Moreover, extrapartition transient data sets are not recoverable. VSAM ESDSs, on the other hand, are recoverable within limitations, and processing is more efficient. The recovery limitation is that records added to an ESDS during an uncompleted UOW cannot be removed physically during the backout process, because of VSAM restrictions. They can, however, be flagged as deleted by a user exit routine.
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