For the sake of this post, I am talking specifically about SQL Server 2012 and higher.
Let’s break this down.
On all editions of SQL Server (Enterprise, Standard, Web, Express), there is a configuration setting called Max Server Memory. This value should not be left at the default 2.1 petabytes, because at that value SQL Server will use all the memory you allow it (plus a little bit more if it needs to), and once it has it, it doesn’t release it back to the operating system without a fight.
Read on to see what Max Server Memory actually includes, as well as additional limitations on editions other than Enterprise.