A join index table has the same properties as a base table except that a join index table cannot be queried directly.
The cardinality of a simple join index is of the same order as its component join table with the highest cardinality, with adjustments for row compression and miscellaneous issues. The cardinality of an aggregate join index is typically much smaller than that of any of its component join tables.
The degree of either type of join index table is dependent on how its definition.
Join index tables have increased disk space requirements. A join index table with fallback protection needs twice the disk space.
The disk resources required for a join index are described in Join Index Storage.