Wanda, Apologies if this was already mentioned (I haven't read this entire thread), but Expiration can have a dramatic impact when the log is pinned. It does not in itself typically pin the log for long periods of time. However, it can exacerbate the situation where the log is pinned, especially when you have logmode=rollforward. The log is actually circular and has a "head" and a "tail". The oldest open transaction pins the "tail" of the log. Any other updates, whether they remain open or not (for rollforward) will move the "head" forward. When the "head" catches up to the "tail", then the log utilization reaches 100%. The faster the head moves in a situation where the tail is pinned, the faster your log utilization will near 100%. Expiration is one thing which can move the head the fastest (IMHO). When I see our logutil rising, the first thing I check is to see if expiration is running, and if so cancel it. This will slow down the rate of increase in logutil. It would be nice if this happened automatically, even before db writes are slowed down, but I don't believe it does.
This may not apply for logmode=normal, I'm not really sure. ..Paul At 04:17 PM 5/15/2011, Prather, Wanda wrote: >Am I correct that scheduling of background processes is important as well? >Don't expiration, migration, backup stgpool also create log transactions? >I'm wondering if it is the housekeeping, rather than the number of client >backups, that is sending my server over the edge. -- Paul Zarnowski Ph: 607-255-4757 Manager, Storage Services Fx: 607-255-8521 719 Rhodes Hall, Ithaca, NY 14853-3801 Em: [email protected]
