Message type: E = Error
Message class:  CNV10400 - Messages for package 10400 (characteristics) 
Message number: 101
Message text: Data element (&) without domain is not allowed
A data element without domain was found
In this Release, data elements without domain are not allowed. The entry
for this data element is incorrect.
Have a look at the entry for this data element in table CNVDOMS.
Error message extract from SAP system. Copyright SAP SE.
The SAP error message CNV10400101 indicates that a data element is being used without an associated domain, which is not allowed in the context of the operation you are trying to perform. This error typically arises during data migration or conversion processes, particularly when using the SAP S/4HANA Migration Cockpit or other data transfer tools.
Cause: Missing Domain: The data element referenced in the error does not have a domain defined. In SAP, a domain defines the technical attributes of a data element, such as its data type, length, and value range. Incorrect Configuration: The configuration or mapping of the data elements in the migration or conversion process may be incorrect, leading to the use of a data element that lacks a domain. Custom Data Elements: If you are using custom data elements, they may not have been properly defined with an associated domain.
Solution: Check Data Element Definition: Go to transaction SE11 (Data Dictionary) and check
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
CNV10400100 *** Messages for analysis part of package 10400 ***
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV10400067 Table &1 will be excluded from the conversion
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
CNV10400102 Initial table name is not allowed
What causes this issue?  Initial table name is not allowedSystem Response  Field TABNAME in table CNVFIELDS must not be emptyHow to fix this error?  C...
CNV10400103 Initial field name is not allowed
What causes this issue?  Initial field name is not allowedSystem Response  Field FIELDNAME in table CNVFIELDS must not be emptyHow to fix this error? ...
Click on this link to search all SAP messages.