Field Symbols – They are placeholder or symbolic NAMES for the other fields. They do not physically reserve SPACE for a field, but point to its contents. It can point to any data objects.
Field-symbols <fs>

Field Groups – Field groups does not reserve STORAGE space but contains pointers to existing fields.
An EXTRACT dataset consists of a sequence of records. These records may have different structures. All records with the same structure form a record TYPE. You must define each record type of an extract dataset as a field group, using the FIELD-GROUPS statement.
Field-groups <fg>

Field Symbols – They are placeholder or symbolic names for the other fields. They do not physically reserve space for a field, but point to its contents. It can point to any data objects.
Field-symbols <fs>

Field Groups – Field groups does not reserve storage space but contains pointers to existing fields.
An extract dataset consists of a sequence of records. These records may have different structures. All records with the same structure form a record type. You must define each record type of an extract dataset as a field group, using the FIELD-GROUPS statement.
Field-groups <fg>