Document type & cannot be stored on this frontend

What causes this issue?

You have tried to store a document of a specific format which is not
available on your frontend, or it is not defined in Customizing that it
is available on your frontend.

System Response

Storage was rejected by the system.


&WHAT_TO_DO& for the system administration
If a document of this format is to be stored, check whether a technical
document class of this format is defined:
<DS:TRAN.OAC2>execute function</>

Error message extract from SAP system. Copyright SAP SE.