> -----Original Message-----
> From: IBM Mainframe Discussion List On Behalf Of John McKown
>
> [ snip ]
> . . .. Take a case in point. A programmer has two VSAM KSDS
> files. He is reading one file sequentially and wants to see in the
second
> file has as associated record in it (both files are keyed
identically). How
> to do that? I will grant that in the past, this was a "no brainer".
However,
> this "normal" (perhaps sub-normal?) programmer did it the "easy" way.
He
> read the first file sequentially. Then, for each record read, he did a
keyed
> read of the second file. The second file contained about 5% of the
number of
> records in the first file. So 95% of the time, the keyed read got a
"record
> not found" and, as a plus, ended up with its buffers flushed and
positioning
> lost.
>
> Of course the correct way to do this is to read each file sequentially
in
> parallel (they are in the same order due to using the "same" key
values),
> doing a "match merge" type operation. But that mindset seems, at least
> around here, to have disappeared. I did the "match merge" code to show
how
> to do it (with a dramatic reduction in CPU and elapsed time). The
programmer
> considered __that__ to be "too advanced" and "obscure".
IBM already provides a program to do exactly that: ICETOOL.
Syncsort provides a similar program. Don't know about CA-Sort.
Why bother to reinvent that wheel?
-jc-
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