From: Oisin McGuinness (oisin@smbc-cm.com)
Date: Tue Nov 25 2003 - 11:42:26 EST
Dear Alpha Managers,
On our Sybase installs on various versions of Tru64 Unix 4.0, we have
been setting (per the Sybase install recommendations), the aio-max-num
attribute in the rt subsystem to a higher value than defaults, e.g., on a 4.0D
system, the default seems to be:
sysconfig -q rt aio-max-num
rt:
aio-max-num = 716
and on one of our database servers:
sysconfig -q rt aio-max-num
rt:
aio-max-num = 2048
(Similarly on 4.0F boxes, which seem to introduce a new parameter aio-socket-on-off = 1)
This tuning recommendation seems to be needed to avoid the Sybase messages
of "dstartio: I/O request repeatedly delayed" when a mismatch between Sybase configs and OS configs exist.
(Sybase's wants/wanted aio-max-num to be greater than max async ios per dataserver.)
Now on Tru64 Unix 5.1, there is no aio-max-num (or aio_max_num) attribute. There is
an aio_task_max_num (as in 4.0x also).
Question 1: What replaces aio-max-num in version 5.x?
Note that there is no man page in 5.1 for sys_attrs_rt. I have also done searches
in the archives of this mailing lists (one summary "SUMMARY: Async IO" June 1 1998 had
an explanation of aio-max-num as "# of outstanding io's in database" from Lars Bro)
and in the news groups. I've also done several searches on the HP documentation
pages (slightly puzzling why there is no best practices or tuning recommendations
for database servers), and found no suggestions or discussions.
Question 2: If there is no longer a aio-max-num, is it essentially unlimited,
and then should we just set aio_task_max_num and be happy?
Oisin McGuinness
SMBC Capital Markets
277 Park Avenue
New York NY 10172
USA
phone: 1-212-224-4913, email: oisin@smbc-cm.com
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