Dear friend,
"Stoppage of increment" means with holding of the sanction of periodical hike in the pay-scale of an employee by the employer/disciplinary authority as a measure of punishment to him for any proven misconduct. It's effect can be of two types depending on the gravity of the misconduct. One is "cumulative" and the other is "non cumulative". "Stoppage of increment for two years with cumulative effect" means increments would not be granted for the next two years and thereafter the sanction would be restored notionally from the stopped stage of the pay-scale so as to cause the loss of two years increment permanently through out the career. In case of non cumulative stoppage, sanction would be actually restored from the stopped stage and the effective loss is only for two consecutive years of service.