log files rotation

Hello,
I currently use a daily rotation for the mathopd log files: 

Log /home/log/mathopd/log.%Y%m%d 

However I recently reached a point where my log files reach the OS max file 
size in one day.
Is there a way I can have mathopd rotate files:
 - on an hourly basis ?
 - on a 15 minutes basis ? 

Also, am I correct if i say that to increase the max file size (under RH 
linux) I would have to overwrite the value in
/proc/sys/fs/file-max
?
Do i have to restart anything for this change to be taken into account ? (i 
realize this is more of a linux question but well :) ). 

Thanks!