SQL Server 2005 high memory usage and performance problems

I have this ASP.NET/SQLServer2005 website running on a production server (Win2003, QuadCore, 4GB).

The site runs smoothly normally, but after 2-3 weeks I notice a slow performance on the site (especifically in one particular page). Also I notice that the SQL Server process is using like 2GBs of RAM. So I restart the service, the site runs fast again and the process 300-400MBs.

I'm looking for an explanation of why is this happening? What is SQL Server storing in RAM that takes too much space and degrade开发者_开发技巧s the performance? What can I do to avoid this? I'm trying to avoid restarting the SQLServer everytime this happens.

Thank you!

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By design: SQL Server is using as much memory as it needs/can. In theory it releases memory on demand but in practice it does not play well with others especially if loaded.

You need separate servers or limit SQL Server memory