Re: RA, bugs, and performance

Carlson@WHSmith wrote: > > As part of my tuning, I was planning to revisit these variables. Where > would be a good trade-off between read-aheads and bufwaits? I've seen > the postings by various people, and took them to heart for the next > round of R&D testing on my test system. The RA parameters do not affect bufwaits. Bufwaits are caused by a thread having to wait for an LRU to unlock so it can write to a BUFFER. It is caused by too few LRUS or just a busy system (or a suspected bug related to how processes select the next LRU if they have to wait too long for the LRU to unlock which happens when LRUS in (16,64,96)). > Unfortunately, bug# 85350 changed all of that. Have not heard of that one. Please elaborate. > I now have reset these parameters to 0. While I didn't mind retuning > these variables, I hadn't planned on resetting them quite like this. Oh NO! > Any idea of what the impact to my system would be? We're a mixed > environment, OLTP and DSS batch reporting. Increased stress on the I/O subsystems, especially if the server is very busy. If the server is dedicated, and not already running close to capacity, you may not notice. If you have to share the machine with other apps there will probably be degradation in both server performance and that of the other residents. Art S. Kagel