ULC Size and Disk I/O

Hi,

We're running Sybase 11.9.2 and recently increased our User Log Cache
(ULC) to 16384 from 2048. Sysmon was showing that well over 20% of ULC
flushes were due to a full ULC (sometimes over 50%). Since the
increase this figure has reduced to less than 1% and the new cache
size is usually fully utilised (on a 1 minute sample)

However, we have also recently experienced what we think are disk i/o
problems. We have occasional high disk activity (high Average service
time (residency)) and "Avg Time per Normal Chkpt" sometimes in excess
of 5 seconds. This can happen for a period of 2 hours roughly twice
per day and causes our apps to run too slowly. There is no known
interference from other processes.

The network guys say that the disks (SAN) are not to blame - and that
we should consider reducing the ULC back to 2048. I'd like a second
opinion before trying this.

Thanks in advance..
Chad.

Server Version: Adaptive Server Enterprise/11.9.2.3/1159/P/SWR 9218
ESD