SAP Note 14203 - Table T399X cannot be maintained via OS35 and SM31

Symptom:

If a customer creates a new client, it may occur that table T399X is empty or incomplete. However, you cannot enter new entries with Customizing transaction OS35 or maintain them via transaction SM31.

Cause and prerequisites

The table was not copied.

Solution
Please use transaction COTB to copy data from client 00. In case it does not exist, use transaction SM29 with command file P21A_c_SFC.