isa

Hi guys,
my problem is this. I'm mananging more than 20000 pages and I'm using mnay PHP scripts to show banners and some stuuf on my pages. I started using some flat text file then I switched to MySQL but I still have problems with my server. It slows down often and my provider seems no to be able to help me. I have a dedicated server really powerful but I think it could be misconfigured. I decide to modify my scripts including a .inc files with data to reduce load on my machine. Do you think it's correct ? Which is difference in reading a flat file or accessing to MySQL table or including a file ?

Any suggestio to reduce load on my server ?
How many calls can be tolerated by MySQL before slowing down ?

Thanks and Kisses
Isa