David:
It is a little more complicated than that.
You have to start tuning the VSAM data set for proper CI size and a
few other parameters.
I believe there is a red book out there called something like
Demystifying VSAM or something close maybe others can come up with
the proper name.
It is a few years old but still right on the button.
Ed
On Oct 4, 2012, at 6:47 PM, David Speake wrote:
One of my application programmers asked for information on design
decision.
Given two files that are not in order by the match key.
Assuming the smaller file has at most one record per possible key
value.
Larger file may have multiple records for some keys and may also
have values
not found in the smaller file.
Assume optimal blocking, buffering, both files, both solutions.
Which is more efficient?
Sort the smaller by that key, load to VSAM, then pass the unordered
larger file and
do random retrievals from the VSAM file.
Sort both PS files by key in question and pass sorted files for
matching by key.
We both (sorta) think the answer is ... "It depends" but on what
criteria?
Number of records in each file? Which is more important? And by how
much?
Record lengths? Same as above?
Length of key field in question? (Within SORT and VSAM length
restrictions of course).
Key bias in larger file?
Ratio of hits/non hits?
Anyone have a nice formula? :-)
David Speake
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