I scheduled a script by using scheduler and action time and expiration time is updating after 10 mins but some time i am not getting any logs for that scheduler.
The scheduler would write to the sm log you have configured for the 'class' of your schedule record. For example if the 'class' was 'problem' you would look in the sm log for the problem scheduler.
Or perhaps you mean your script is supposed to write to the log but you do not see the script messages? In that case it could be logic error in your script.
As I mentioned you are either looking in the wrong log or there is a probelm in your script.
I would need to know the class of your schedule record, the sm.cfg file where you start the scedulers ( since this can dictate which log to look at). your sm.ini file (again to see where your log is) and your script to check for logic/coding errors.