It's the supportlink backup system. The backups took too long. When they task fails, Lab Manager doesn't clean them up very well (or at all).
Use Management studio express to delete them.
Then please update the the following stored procedure, which should help in the future.
-- Drop the old View and create new
IF EXISTS (SELECT * FROM sysobjects WHERE type = 'P' AND name = 'DeleteOldActivityLog') DROP PROC DeleteOldActivityLog
GO
-- Deletes the Old Activity Logs from the table based on a date.
CREATE PROCEDURE [dbo].[DeleteOldActivityLog]
-- Add the parameters for the stored procedure here
@deleteDate datetime
AS
BEGIN
-- To clear Jobs after deleteDate to resolve Constraint Error. This number will be very less
DELETE FROM Jobs WHERE starttime >= @deleteDate and root_job_id IN (SELECT job_id FROM Jobs WHERE starttime < @deleteDate)
-- Clears Jobs. After the above statement, This should not give any error
DELETE FROM Jobs WHERE starttime <@deleteDate
RETURN 0
END
go