Looking at the memory limits and other limits on the SQL Server versions over time, we have seen things increase, but one limit that is still very low is the memory limit for SQL Express. Specifically the maximum memory for buffer pool per instance of SQL Server Database Engine for SQL 2019. The limit there is 1410 MB.
At first glance you may think that this limit is the total amount of memory that SQL Server will use, but let me show you a couple of screen shots for Database Health Monitor showing the memory utilization on two different SQL 2019 Express servers.
With both of the screen shots above if you start adding up what is in the Memory (mb) column, you can see that it quickly exceeds the buffer pool limit of 1410 mb. On the first server the plan cache alone exceeds that limit. So what exactly is limited by the 1410 mb buffer pool limit.
The 1410 mb buffer pool limit refers to the buffer pool, or the amount of database pages that are loaded into memory at any 1 time. On the first diagram, SQL Server is using over 3gb of memory, but the size of all the databases marked in the blue highlight does not exceed that 1410mb size.
On the second diagram when you add everything up, the total memory is approaching 3gb, but the rows highlighted in blue do not exceed the 1410mb size. They do come very close, but they do not exceed it.
When you are working with SQL Server Express edition and you are trying to size things correctly, don’t assume that it will only be using that 1410mb size, or on older Express versions the 1gb size limit. There are other parts of the database that will use more memory if it is available.
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