ORA-12899: value too large for column COMESFROMTOWN (actual: 50, maximum: 50)
Thanks to Wernfried Domscheit suggestion, this solved the issue :


ALTER SESSION SET nls_length_semantics = CHAR which was decisive
CHARACTERSET WE8ISO8859P1 which exactly fits the source file characterset


Note that our Oracle 11g instance is configured with following defaults:


NLS_LENGTH_SEMANTICS = CHAR 
NLS_CHARACTERSET = UTF8