RE: USEOSTIME and performance

>---------- From: satriguy@aol.com[SMTP:satriguy@aol.com] >Sent: Tuesday, February 24, 1998 2:10 AM >>I have been asked to check the performance differences between USEOSTIME >>on and off. I expected the that there would be a slightly better >>performance (4-5% according to manual) with USEOSTIME = 0/No. This >>isn't the case on the tests done, in fact it is exactly the reverse. >>With USEOSTIME set to 1/Yes it is consistently better by 4-5%. >> >>The test script is a simple insert into a temp table, no time information used. >If the table does not make use of any "time" column, then the impact of >USEOSTIME would not come into effect. The difference in the time would be due >to some other factor, possibably some key pages already in the bufferpool. I think each SQL statement which is executed determines the current time when it is started in case any stored procedures or the like are called while the statement is executing and these refer to CURRENT. So, I don't think it matters whether the statement itself explicitly references time - the values of CURRENT has to be determined anyway. I'm not sure why there is the claimed performance degradation, but I suspect it is o/s specific. Somewhere out there in Unix-land there is an o/s where the gettimeofday() or equivalent sub-second time system call takes a long time. It needn't be true on all platforms. The testing supports this hypothesis, but is hardly conclusive. I'd trust measurements of performance over the documentation. Yours, Jonathan Leffler (jleffler@visa.com) #include <bother.ms-exchange.h>