Drigg website using too much memory after 2 years online and too many nodes and terms, reason ?

Hi,

Do you have any idea why a drigg website can show more and more error pages after getting big and old ?

I have thousands of drigg nodes and terms (taxonomy) and without changing anything i now get hundreds of errors everyday.

My host said that the website shows error pages because it's using too much memory, so what can I do ?

I wonder if I should clear some tables or do anything else ?

Thanks for help.