VM only allows one I/O per disk at a time. If this is a CMS mini disk then there
will be no impact as CMS mini disks are not normally shared for write by
multiple users. Disk cache will probably hide an effect on read sharing. If it
is a Linux disk then there is no impact because Linux doesn't like shared dasd.
VSE may be impacted by the one I/O limitation. As VSE is also limited to one I/O
per disk the impact will be in VSE not in VM unless the volume is shared by
multiple VSE guests. With MVS guests it gets very complicated because of PAV and
other considerations.
So the answer is maybe.
I found that for VSE VSAM volumes 3390-9 volumes allowed larger files without
impacting performance. However, if you tried to combine several VSAM catalogs
into one by placing more files on a volume that had a negative impact on
performance.
[EMAIL PROTECTED] wrote:
I have a question that pertains to performance.
We currently have 3390 mod 3 defined volumes. The customer requires a
larger mini disk size than what will fit on a 3390 mod 3. We are planning
to create 3390 mod 9s for their larger mini disks. Would someone explain
the performance hit that will occur by placing their data on a larger
volume. Maybe it is insignificant, but I seem to recall the architecture
permits a limited number of accesses to the device. If there are a large
number of users who require access at a given time, then the users could end
up waiting for the device?
Please advice.
Thank you.
Cecelia Dusha
--
Stephen Frazier
Information Technology Unit
Oklahoma Department of Corrections
3400 Martin Luther King
Oklahoma City, Ok, 73111-4298
Tel.: (405) 425-2549
Fax: (405) 425-2554
Pager: (405) 690-1828
email: stevef%doc.state.ok.us
