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BUFNO and number of records in sequential files

 
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Baskaran
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PostPosted: Tue Oct 24, 2006 3:34 pm    Post subject: BUFNO and number of records in sequential files
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IS there any relation for parameter BUFNO in jcl and number of record read from a sequential file in a job?

for performance point of view is there any standards to be followed for coding BUFNO in realtion with sequention file content(number of records)
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dbzTHEdinosauer

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PostPosted: Tue Oct 24, 2006 6:53 pm    Post subject:
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IS there any relation for parameter BUFNO in jcl and number of record read from a sequential file in a job?


No. The number of records read by a STEP (since BUFNO is a DD parameter; DD parms are part of a STEP, not a JOB) depends upon what the STEP does. The BUFNO parm indicates - number of blocks read during a physical I/O.

Quote:
for performance point of view is there any standards to be followed for coding BUFNO in realtion with sequention file content(number of records)


Standards are set by sites. Have no idea what your site standards are. Since buffers are usually allocated below the 16M line, and sites have standards concerning how much lower memory can be allocated to a JOB, you need to learn about your site standards.

Now, if your question is: 'are there things that need to be taken into consideration when determining the BUFNO value with respect to performance' - yes. A buffer contains a block. If you allocate enough buffers to load the complete file in memory, the physical I/O performed with the first read will load everything; subsequent reads will effectively be repositioning of record pointers in memory.

You also need to take into consideration, what else occurs during this STEP.

your question is so general that it will only elicit general answers.
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Baskaran
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PostPosted: Wed Oct 25, 2006 11:21 am    Post subject: BUFNO and number of records in sequential files
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Thanks Dick Brenholtz

We a job which does unlod records from Db2 table into a GDG and then performs a SORT and then load it in to a different table.during unloding, records are filtered by a SQL statment.


My question how we should do performance tuning for this senario.
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amalraj_ece

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PostPosted: Mon Oct 30, 2006 7:16 pm    Post subject: Re: BUFNO and number of records in sequential files
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Normally the BUFNO specifies how much amount of virtual storage is going to be allocated for that step
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