Effective SQL Server administration involves not allocating all RAM to SQL Server to ensure system stability, keeping SharePoint databases in a separate SQL instance for performance management, and turning off auto-update on your servers to maintain control over when updates are applied.
Microsoft SQL Server is made to use all the available memory in a server for itself. It will eat all the memory you throw at it. This can be a problem because your other applications may suffer performance problems as all the system memory is gone. To limit this behaviour you can limit the maximum amount of memory SQL is allowed to use.
Because SharePoint server will create quite a few databases, it’s easier to manage them in a separate SQL instance rather than mixing it with other system’s databases:
It is not a good idea to have Windows Update automatically updating your servers. There are a few reasons.