I was asked this question recently and I couldn't find the answer or any detailed explanation on the internet regarding this. Can anyone please explain or provide a reference link that explains about the component of SQL Server architecture that handles the user login requests?

Thanks in advance!!

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    You're looking largely at SQLOS for the initial connection to the SQL Server itself for authentication and some authorization such as some server level objects, then the Database Engine for authorization for lower level requirements. I don't have a breakdown or concrete answer to reference however. Dec 18, 2017 at 21:45

1 Answer 1


There is not a dedicated "component of the SQL Server architecture" for this. The protocol layer, including the whole login process is handled by the Database Engine. The SQL Server Database Engine is a single large process that hosts

"the protocol layer, the query processor (also called the relational engine), the storage engine and the SQLOS."

--Microsoft SQL Server 2012 Internals, pp 10 Kalen Delaney, et al

This is in contrast to Oracle, which has the "Oracle Net Listener" which is a separate process. https://docs.oracle.com/cd/B28359_01/network.111/b28316/architecture.htm#NETAG209

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