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.
Example
FIELD-GROUPS: HEADER, ORDER, PRODUCT.
Note
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.