Schema segments automatically map a c-tree field type to a key segment type (mode). Starting with V8.14, CT_CHAR fields are now treated as a signed, one-byte integer, whereas, previously, they were treated as a REGSEG segment mode. CT_CHARU remains treated as an unsigned one-byte field.
To revert this change for compatibility with versions prior to V8, use the COMPATIBILITY CHAR_SCHSEG server configuration keyword.
COMPATIBILITY CHAR_SCHSEG