Rick Fochtman wrote:
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I'm afraid I disagree.
Because you are confusing the DSCB with the blocks written in the
dataset.
We are arguing semantics ...
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NOT HARDLY!
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What it proves is not that the DCB on DASD was overwritten by the
one in the JCL, but that the DCB in the JCL was
incorrect/incompatible with the one on DASD.
Why would you get an I/O error if the DCB information on the DD
statement did not take precedence over that in the DSCB?
Why would a square peg not fit in a round hole if the round hole did
not take precedence over the square peg?
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If the attributes in the JCL are equally wrong, you'll still get that
I/O error.
... because the DCB on DASD takes precedence over any coded in the JCL
or in the program, in that order. The DCB attributes on DASD have the
'final say' in whether an input I/O will complete successfully. That a
program can populate its own DCB from the JCL's DCB attributes, and then
open it for input *before* having to deal with the real DCB on DASD, is
irrelevant if the JCL DCB's attibutes are inconsistent with those of the
physical dataset on DASD. It is the physical dataset's DCB attributes on
DASD, and not those of the DCB opened by the program, which determine
whether the I/O is successful. If those of the program's opened DCB do
not match those of the physical dataset on DASD, the I/O fails - because
the DCB on DASD 'overrides' (or 'takes precedence over' etc.) the DCB in
the program when it is opened for input and the program then issues a read.
Much of this 'discussion' has been akin to arguing that a bridge made of
string and bamboo was correctly designed because, when a car tried to
cross over it, the bridge broke and the car fell into the ravine ... and
the car could not possibly have fallen into the ravine if the bridge had
not been hanging across it in the first place - "QED".
Read up on the handling and formats of FIXED vs. VARIABLE vs.
UNDEFINED records. What you apperantly don't know CAN hurt you!
I don't need to be distracted by reading other people's opinions when I
can think for myself. What I don't know can indeed hurt me - but what I
know can't.
Cheers, Chris
Rick
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