On 22/05/2013 4:11 PM, Miklos Szigetvari wrote:
Hi
Maybe some point:
- A few years ago in the OMVS newsgroup somebody pointed out that the
"fseek" "ftell" etc could decrease the performance very drastically
- If you need a random access maybe the VSAM would be an option
IIRC, that would be if you opened that dataset as a QSAM file as apposed
to BSAM, which is the default. Of course, even with BSAM you need to do
a fgettpos()/fsetpos() etc.
My testing has shown that the UNIX file system considerably outperforms
legacy datasets for reads and writes. My tests may be flawed but they
consisted of reading/writing 4k blocks.
On 21.05.2013 16:24, Bernd Oppolzer wrote:
We already have improvements to cut the open/close/free overhead.
The ca. 800 little tables are put into 8 large containers, which have
a (sort of) directory at the beginning, so that there is only one open
for the container. The open is done only once, and the containers stay
open throughout the whole process (all day long). So open/close/free
is no concern. Same goes for Windows/Linux/Unix.
I have still to examine if the z/OS record sizes fit well to the
fread sizes.
I did not do the customization to z/OS, only the original design for the
other platforms. z/OS Unix is an option, but there are customers out
there, that want the files to be "classic" OS files.
(there are 18 different platforms where this applications runs on,
including Solaris and BS/2000).
Kind regards
Bernd
Am 21.05.2013 14:38, schrieb Paul Gilmartin:
On Tue, 21 May 2013 09:55:51 +0200, Bernd Oppolzer wrote:
Slightly drifting topic:
We use fseek / ftell / fread to do the file I/O. The files are
normal sequential
OS files.
Sounds like the worst of both worlds. Have you tried it with normal
z/OS UNIX files? The kernel may do the caching for you.
I've found that for large numbers of small files z/OS UNIX files
vastly outperform legacy data sets. The allocate/open/close/free
overhead is brutal.
-- gil
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