From everything I read setting the max server memory to a reasonable capped limit is a best practice to support effective performance and relaibility of your SQL Server. However, I have seen a few discussions saying that althrough SQL will use lots of memory, it can easily release it to the OS if the OS requires it for OS operations. If that is genuinely the case, why do you need to cap the amount of memory SQL can use, if when the OS needs memory resources SQL will release them?