roll over does not happen when iis application pool recycle

[Guanrao Chen]

hi, guys

the hourly roll over is OK most of the time; only for one hour when the 
server's application pool recycle the expected roll over file never shows up.

for example:
mylog.20080901-00
mylog.20080901-01
mylog.20080901-02
mylog.20080901-03 <- this one never shows up and iis recycle happens at 03:XX
mylog.20080901-04
...

any idea?

thanks,
rao