FIELD-GROUPS fg.
Defines a field group.
A field group combines several existing fields together under one name.
You use the INSERT statement to determine which fields belong to a field group at runtime.
FIELD-GROUPS: HEADER, ORDER, PRODUCT.
Neither defining a field group (statically) using FIELD-GROUPS
nor filling a field group (dynamically) with INSERT generates
more memory. Rather, there exists for each field group element a pointer to an (existing) field.
See You cannot define field groups in methods.
Defining Extracts