// Start Transaction Example 1
txnAborted = false;

// Start a session.
session = db.getMongo().startSession( { mode: "primary" });

employeesCollection = session.getDatabase("hr").employees;
eventsCollection = session.getDatabase("reporting").events;

// Start a transaction for the session that uses:
// - read concern "snapshot"
// - write concern "majority"
session.startTransaction( {
   readConcern: { level: "snapshot" },
   writeConcern: { w: "majority" }
} );

try{

   employeesCollection.updateOne( { employee: 3 }, { $set: { status: "Inactive" } } );
   eventsCollection.insertOne( { employee: 3, status: { new: "Inactive", old: "Active" } } );

} catch (error) {
   txnAborted = true;
   print ("Abort transaction.");
   session.abortTransaction();  // Uses write concern "majority"
}

// Until commit, no data changes from the two operations in the transaction are visible outside the transaction

if (!txnAborted) {
   print ("Commit transaction.");
   session.commitTransaction(); // Uses write concern "majority"
}

session.endSession();

// End Transaction Example 1