Field &1 ignored: Data type &2 not allowed for characteristic

What causes this issue?

Characteristics can be used in Analytics in the Group By and for
filtering. The Analytic Engine can only map fields to a characteristic
if the data type is none of the following: binary, a string/blob, a
figure like DEC or FLOAT.
Field &V1& is therefore ignored and is not part of the analytical model.

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?

Usually fields which represent a figure should be mapped to a key
figure. Key figures need a defined default aggregation. You should
therefore add the CDS annotation "@Aggregation.default". Standard
default aggregations are #SUM, #MAX, or #MIN. If the field can't be
aggregated, for example because it is a price in an analytic dimension,
aggregation #NOP can be used. This means that the aggregate is equal to
the value of the record if the aggregate contains just one record. It is
the exceptional value "NOP" if the aggregate contains more than one
record.
If the field shouldn't be used in the analytic model or can't be used
because of an unsupported data type, it can be suppressed with the CDS
annotation "@Analytics.hidden. true".

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.