Here's an excellent
real life example of why BCHR is not a good tuning metric and you should focus
on reducing I/Os.
A simple fix for a
query and here is the resulting email to the client, who understands that BCHR
is not good. A little techie humor...
I have good news and I have bad news.
The good news is that the elapsed query time and total I/Os for the latest iteration dropped significantly.
Old --> 1:42 min 2,715,659 i/os (15,925 physical)
New --> 22 seconds 3318 i/os (2861)
However, the bad news is that the Buffer Cache Hit Ratio dropped dramatically!
Old --> 99.36%
New --> 13.77%
So, I have undone all the changes I made and will begin looking at other methods to improve performance!
