Thanks for your help

but I am so confused about the setting the max server memory for SQL with the right value.

I read the Memory Management chapter of Jonathan Kehayias ebook:

"if the server only has 4 GB

of physical memory (RAM) installed, that's going to be the upper limit for SQL Server.

If a server has 64 GB of RAM, and the Windows operating system is Windows Server 2008

64-bit Standard Edition, then the OS limit is 32 GB and that is the most that could be

used by SQL Server."

and also

From this ebook I understand that "SQL Server will use as much memory as you can give it, and it will not release the memory that it has allocated under normal operations, unless the operating

system has set the memory low resource notification flag" but I can't understand how does he calculate the max server memory option!!!

What happen if I set it to the value that is grater than the physical memory (RAM) installed???

In this case how much memory does sql consume?