On Tue, 2007-11-13 at 14:36 -0500, Greg Smith wrote: > On Tue, 13 Nov 2007, Andrew Sullivan wrote: > > > I have to agree with what Tom says, however, about people thinking > > they're smarter than the system. Much of the time, this sort of thumb > > on the scale optimisation just moves the cost to some other place > > Sure, but in this case the reasoning seems sound enough. The buffer > eviction policy presumes that all buffers cost an equal amount to read > back in again. Here we have an application where it's believed that's not > true: the data on disk for this particular table has a large seek > component to it for some reason, it tends to get read in large chunks (but > not necessairly frequently), and latency on that read is critical to > business requirements. "The system" doesn't know that, and it's > impractical to make it smart enough to figure it out on its own, so asking > how to force that is reasonable.
It seems possible to imagine a different buffer eviction policy based upon tablespace, block type, peak rather than latest usage pattern etc.. -- Simon Riggs 2ndQuadrant http://www.2ndQuadrant.com ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
