MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 11: Integrated Indexes

Updating Index Rows

When the consumer updates, deletes, or inserts a base table row with IRowsetChange, the provider automatically updates, deletes, or inserts the corresponding entries in all integrated indexes associated with the base table. In other words, for integrated indexes, DBPROP_INDEX_AUTOUPDATE is always VARIANT_TRUE.