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Tape vs. DASD - speed/time/CPU utilization difference

 
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GaneshMF

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PostPosted: Wed Feb 10, 2010 3:32 pm    Post subject: Tape vs. DASD - speed/time/CPU utilization difference
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Hi,

Will there be any processing speed/time/CPU utilization difference when reading and writing a file in the below given two cases,

1) a tape file
2) a PS file in DASD.
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PeterHolland

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PostPosted: Wed Feb 10, 2010 3:34 pm    Post subject:
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What do YOU think?
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GaneshMF

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PostPosted: Wed Feb 10, 2010 3:41 pm    Post subject: Reply to: Tape vs. DASD
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I face few processing time difference between them..
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PeterHolland

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PostPosted: Wed Feb 10, 2010 3:43 pm    Post subject:
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Like ?

DASD faster or slower compared to tape?
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GaneshMF

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PostPosted: Wed Feb 10, 2010 3:46 pm    Post subject:
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Ya when i ran a job with file in DASD , it ran faster than when i ran it with tape file as input..
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GaneshMF

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PostPosted: Wed Feb 10, 2010 3:47 pm    Post subject:
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Is there any way to speed up the read/write process in tape??
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PeterHolland

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PostPosted: Wed Feb 10, 2010 3:53 pm    Post subject:
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Fast tape units, blocksize, maybe tapes are mounted manually.

But DASD processing is always faster in normal sequential processing,
but then direct tape processing is (except "stress" testing) never done.
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GaneshMF

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PostPosted: Wed Feb 10, 2010 3:55 pm    Post subject:
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[quote="PeterHolland"]Fast tape units, blocksize, maybe tapes are mounted manually.

What is it, 'FAST TAPE UNITS' ?
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PeterHolland

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PostPosted: Wed Feb 10, 2010 3:57 pm    Post subject:
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Google on 'FAST TAPE UNITS' and you will get lots of answers.
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GaneshMF

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PostPosted: Wed Feb 10, 2010 4:02 pm    Post subject:
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Thank you!!
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Bill Dennis

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PostPosted: Thu Feb 11, 2010 9:52 pm    Post subject:
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No tape mount will match DASD allocation speed. The fastest is probably a scratch mount in a virtual tape server (usually < 5 secs.). Next is scratch mount from an auto-loader.
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kailas girase

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PostPosted: Fri Feb 12, 2010 12:33 pm    Post subject:
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Tape Data sets not accessible for COBOL programmes, But DASD can be.

Tape is magnetic device, while DASD is optically written data.

I am not sure on above, some clarifications are expected.
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dick scherrer

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PostPosted: Fri Feb 12, 2010 12:55 pm    Post subject:
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Hello,

Why would you believe that tape datasets cannot be used by COBOL programs? Of course they can. . .

Quote:
Tape is magnetic device, while DASD is optically written data.
And this was posted because . . .?
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Robert Sample

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PostPosted: Fri Feb 12, 2010 5:43 pm    Post subject:
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Quote:
Tape Data sets not accessible for COBOL programmes, But DASD can be.

Tape is magnetic device, while DASD is optically written data.
I count at least three mistakes and one clarification in your two lines:
1. Tape data sets are easily accessed by COBOL programs.
2. DASD data sets are also easily accessed by COBOL programs.
3. Tape data is written magnetically, however the device itself is not a magnet -- it is a complicated piece of machinery that accepts electrical impulses from the CPU and translates them into magnetic bits written upon the tape
4. DASD is not optically written. DASD data is magnetic bits written upon a substrate, just like tape data is magnetic bits written upon a substrate. CD and DVD devices are optical but they don't interface much to mainframes.
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