I frequently am trying to determine how much RAM I can give to SQL Server without starving the OS. Since my servers usually only have SQL Server on them and no other applications, I can give them everything except 2-4gb for the OS. Depending on what that server is doing and if it still looks hungry, I will give the OS more or SQL Server more. The question is, if I can’t remote on to the server, how do I know how much RAM is on the server? After much searching and calculating, I have come up with a T-SQL query to help. It will tell you how much RAM is on your instance.
SELECT physical_memory_kb * 9.5367431640625E-7 FROM sys.dm_os_sys_info
It uses the system views which I haven’t begun to scratch the surface of their awesomeness, but plan to learn more.