A DBCS-only string consists of only DBCS characters. A mixed SBCS/DBCS string is formed by a combination of SBCS and DBCS characters. In EBCDIC, the SO and SI bracket the DBCS data and distinguish it from the SBCS data. Because the SO and SI are needed only in the mixed strings, they are not associated with the DBCS-only strings.
DBCS-only string -> .A.B.C
Mixed string -> ab<.A.B>
Mixed string -> <.A.B>
Mixed string -> ab<.C.D>ef