Group-Level Index Element (IEL) structured field
If INDEXOBJ=GROUP is specified, ACIF creates an index object file with this format:
BDI IEL Groupname=G1 TLE ... TLE ... IEL Groupname=Gn TLE ... TLE EDI
This format is useful to reduce the size of the index object file, but it allows manipulation only at the group level; that is, you cannot obtain the offset and size information for individual pages. You also lose any indexing information (TLEs) for pages; the TLE structured fields for the pages still exist in the output print file, however.