I'm asking this question "for a friend"... personally, I've learned this lesson well:
"Don't! [whack] mess [whack] with [whack] minus [whack] gn!"
Seriously, this was posted as a comment on my blog...
for dbsrv10/dbsrv11 with -gn option what is the max number that we can set? is there any performance hit by increasing number of concurrent server requests.
asked 31 Jul '10, 10:14
The maximum gn value (aka multiprogramming level) that you can set is going to vary depending on:
Increasing the gn value arbitrarily is definitely a bad idea. As you increase gn you may initially see an increase in total throughput but then you will see a decrease in overall performance as the server sees increased contention for resources (e.g. row locks).
Version 12 contains a new feature called "automatic multiprogramming level tuning" and it is on by default. This feature in the server automatically adjusts the gn value of your running server to best suit the workload on the server at that time. The server continuously monitors the workload and total throughput (number of completed requests) and will do this adjustment every 30 seconds. This paper talks more about how this works. You can read more about this feature and other new features in SA 12 here.
answered 31 Jul '10, 13:09