How To Fix UCT8256 - Cannot derive selection for source field &1

SAP Error Message - Details

• Message type: E = Error

• Message class: UCT8 - Message class for UCT8(mapping)

• Message number: 256

• Message text: Cannot derive selection for source field &1

What causes this issue?

The selection for source field &V1& cannot be determined. The selection
is required for one of the following reasons:
The following applies if this is a <ZH>warning message.</>
Source field &V1& is status-relevant - such as the consolidation unit,
document type, version, or one of the higher-level fields. Selections on
these types of fields reduces the volume of the source data being read.
This can dramatically increase system performance during task execution.
For other types of fields, the system needs to read much more,
unnecessary source data, most of which is disregarded during processing.
The following applies if this is an <ZH>error message.</>
A selection for source field &V1& is needed to determine the context
whenever the mapping settings or the source selection of the method
contain a source selection for hierarchies or attributes. See also error
message UCT8 007, which is also displayed with this error message.
The selection for source field &V1& is derived from the target selection
and the mapping rule. In this case, one of two problems apply: (a) the
source selection cannot be derived from the mapping rule that contains
&V1& as the source field; or (b) there is no mapping rule that contains
source field &V1&.

System Response

If this message is issued as a <ZH>warning, </>you can save the
settings. However, you might encounter performance problems during
execution.
If this message is issued as an <ZH>error</>, you cannot save the
settings and the system displays the details of the source selection for
hierarchies or attributes incorrectly. The method cannot be executed at
runtime.

How to fix this error?

Check if a mapping rule exists that contains &V1& as a source field. If
no such mapping rule exists, define one. Otherwise, check any other
messages that may have been issued and modify the mapping rule
accordingly.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.