DataSource not unique

What causes this issue?

Several entries were found in database table /SAPAPO/TSAREAEX for the
specified DataSource (&V1&). Therefore, it cannot be assigned to a
unique planning area.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Specify a planning area for your DataSource so that the check can be
made.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.