startSession

Definition

startSession

New in version 3.6.

The startSession command starts a new logical session for a sequence of operations.

Tip

In mongosh, this command can also be run through the Mongo.startSession() helper method.

Helper methods are convenient for mongosh users, but they may not return the same level of information as database commands. In cases where the convenience is not needed or the additional return fields are required, use the database command.

Compatibility

This command is available in deployments hosted in the following environments:

• MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

• MongoDB Enterprise: The subscription-based, self-managed version of MongoDB

• MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB

Syntax

The command has the following syntax:

{ startSession: 1 }

To run startSession, use the db.runCommand( { <command> } ) method.

db.runCommand( { startSession: 1 } )

Behavior

If the deployment enforces authentication/authorization, you must be authenticated to run the startSession command. The user who runs startSession owns the created session, and only that user can use the session.

If the deployment does not enforce authentication/authorization, a created session has no owner and can be used by any user on any connection. If the user authenticates and creates a session for a deployment that does not enforce authentication/authorization, the user owns the session. However, any user on any connection may use the session.

If the deployment transitions to auth without any downtime, any sessions without an owner cannot be used.

A session can only be used with the MongoClient object that created the session. A single session cannot be used concurrently. Operations that use a single session must be run sequentially.

Output

In addition to the status and operation time of the command, the startSession returns the following session specific information:

id: { id: <UUID> }