The conversion is not explicitly defined

What causes this issue?

Field &V4& of table &V3& does not have a corresponding entry in table
&V1&. In addition, a rule is not defined in the conversion table view
to tell the system how to process this field.

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?

Note the above statements.

Error message extract from SAP system. Copyright SAP SE.