On 2/6/2023 11:31 pm, René Jansen wrote:
What I remember of it is that he was convinced it was a lot slower.
He was mistaken! I've tested it out, and QSAM is no match for zFS. You
can find the details in this gist:
https://gist.github.com/daveyc/14b45d6d70d8dd9af1848e539d78881f. Adding
an fsync() call after writing each record barely incurs any overhead.
zFS, operating with highly optimized Media Manager APIs, handles it
efficiently. Additionally, zFS functions as a caching file system.
I have observed a certain degree of snobbery among many traditionalists
when it comes to USS. I can recall an incident from approximately 15
years ago when I advocated for the use of sqlite in one of our products.
My boss dismissed the idea, expressing concerns that customers might be
deterred by using the UNIX file system. Consequently, we opted for a
VSAM KSDS, despite its inherent limitations. Interestingly, it is worth
noting that there are now numerous IBM z/OS products that embrace
sqlite, with some even integrating it with HLASM.
So I told him that nobody forced him not to use QSAM for datasets just because
it ran in USS. And it think that is a great asset of it. Just because Unix
forces you to have a hierarchical directory system does not mean, in USS, that
you need to use it for all I/O.
René.
On 2 Jun 2023, at 17:03, Seymour J Metz<[email protected]> wrote:
Dubbing is part of the setup overhead for a task, and only occurs once, so
except for very short tasks it is just noise in measuring performance.
As for the general overhead of Unix System Services, the Devil is in the
details. For a comparison to be reasonable, the two programs have to be using
the services in a comparable fashion. Was your COBOL programmer really
comparing the overhead of conventional access methods to Unix file I/O, or were
the numbers drowned out by, e.g., differences in application logic?
--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
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