SQL Server Jobs run in the security context of the account assigned to SQL Server Agent. We want to run a particular step of a job in a different security context. The answer is SQL Agent Proxy.
All the jobs run with the account assigned to SQL Agent service. What if we have to perform some task which requires some extra credentials or the other way around, then what should we do. The answer is SQL Server Agent Proxy. Proxy is about having additional security.
This is a SQL Server Object with already defined functionality. They are to provide limitation to the functionality provided to a proxy. A proxy can be defined with one or more sub-systems. The list of sub-systems is as follows:
Replication Queue Reader
Replication Transaction-Log Reader
SQL Server Analysis Services Command
SQL Server Analysis Services Query
SQL Server Integration Services Package
To access the specified sub-system, the proxy has to use the security context of a Windows User.