On 11 Αύγ, 13:32, iainm <iain.mcne... at (no spam) sqa.org.uk> wrote:
I have two identical databases, one of which is a copy made by using
the checkpoint of the first and rolling it forward. They are on
different machines but the archietecture and set up is almost
identical. The tables have the same structure and statistics and the
rollforward takes place on a nightly basis.
The problem I have is that a query runs on one of the machines almost
5 times faster than the other. The QEP for both is the same, yet when
I use qe90 the actual cpu time taken is over double on one of the
machines than the it is on the other. The ed and ad figures are about
the same. Can anybody give me a pointer on how to go about resolving
this?
[snip]
There is an article called 'A Procedure to Identify and Fix
Longrunning Queries' at the North American Ingres Users Association
site
http://naiua.org/longrunning.php that suggests that the CPU
statistics are not something to be concerened about;quoting :
"When you generate a QEP, you get estimates for Disk I/O (D) and CPU
statistics (C). The CPU statistics are basically useless - you are
concerned with the number of Disk I/O's required. The smaller the
number, the faster the query. It is important to compare the actual
disk I/O required versus the estimated disk I/O."
How did you do the benchmark? If it is 5 times faster then the
bottlneck could be somewhere else
