With only one server, SBS, Directory connector (The SSO Agent) uses a lot of resources.
Directory connector will use as many resources as necessary to respond to the SonicWall’s queries. Installations with more than a few hundred users logging in simultaneously should install multiple SSO agents.
However, there was a known issue in previous versions of the agent which had some specific deployments holding onto allocations of memory for a period of time longer than necessary. This was resolved in 3.6.25 of Directory Connector, which was released back on March 12th, and was made available in the release notes.