The  sessions commands are:

• endSessions
  • adds the sessions to the mongod's LogicalSessionCache's _endingSessions
  • the config.system.sessions docs will be removed the next time the mongod does its periodic LogicalSessionCache refresh
• kill*Sessions
  • aborts the transactions associated with the session
  • closes open cursors associated with the session
  • kills operations associated with the session
• refreshSessions
  • updates the session's "lastUse" in the mongod's LogicalSessionCache
  • the config.system.sessions docs will be updated the next time the mongod does its periodic LogicalSessionCache refresh
• startSession
  • generates a UUID for the session
  • adds the session to the mongod's LogicalSessionCache
  • the config.system.sessions doc will be inserted the next time the mongod does its periodic LogicalSessionCache refresh
  • returns the UUID