An expandable group expression is a list of entries which can contain any of:
Field name
Expandable group name
Alphanumeric or numeric literal
System variable
Expandable group special value, which can be any of the following:
ALL, specifies that all fields from the currently active version of the file in context be expanded in the field list.
ALL_REAL, specifies that all real fields from the currently active version of the file in context be expanded in the field list.
ALL_VIRT, specifies that all virtual fields from the currently active version of the file in context be expanded in the field list.
EXCLUDING, specifies that fields following this special value must be excluded from the field list.
INCLUDING, specifies that fields following this special value must be included in the field list. This special value is only required after an *EXCLUDING entry has caused the field list to be in exclusion mode.
The special values *ALL, *ALL_REAL and *ALL_VIRT are only valid in the context of a file (e.g. when fetching a record using the FETCH command.)
The usual parameter restrictions also apply. For example, the FIELDS parameter of the FETCH command doesn't allow constants or system variables.