The customer carries out this step.
You must block the system for normal activities while the conversion is being prepared and carried out. Documents must not be posted or processed, and master data must not be changed, otherwise your accounting documents and system settings may contain serious discrepancies.
If it is not possible to take measures to ensure that there are no users working in the system, you should block the users and the whole system throughout the organization.
Restart the SAP System so that all users are logged off.