The MS code allows an alternate sort sequence to be defined for sort fields.
Use of the MS code is only relevant when used in a field 8 pre-process code and applied to a field that is specified in a sort clause. In all other cases it will be ignored.
The sort sequence to be used is defined in a special record named SEQ that you must create in the ERRMSG file. Field 1 of this record contains a sequence of ASCII characters that define the order for sorting.