Fields &1 and &3 are incompatible

What causes this issue?

Field &V1& from operating concern &V2& and field &V3& from operating
concern &V4& are incompatible because the data types do not match or
because the field length of field &V1& is greater than that of field
&V2&. This inconsistency could potentially result in a loss of data.

System Response

The fields cannot be assigned.

How to fix this error?

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.