In order to lock an old user account:
Log in as any user who has access to this Maintain Operators section. If you do not have access to this, please contact your on-site Delta administrator.
Select the User Maintenance tab at the top of Delta.
Hit the Maintain Operators.
Open the User you which to lock
Tick the Locked tick box.
Tick the Marked for Delete tick box.
Press OK to save.
This user will no longer be able to log in to Delta. You will be unable to delete a user from Delta if they have done any transactions in Delta.