Index-Organized Table and Bitmap indexes

Bitmap indexes on index-organized tables are supported, provided the index-organized table is created with a mapping table. This is done by specifying the MAPPING TABLE clause in the CREATE TABLE statement that you use to create the index-organized table, or in an ALTER TABLE statement to add the mapping table later.

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Oracle10g Locally Partitioned Bitmap Indexes on an IOT Partition
Bitmap indexes can also be created on partitioned tables as long as they are local to the partitioned table; they cannot be global indexes. Global bitmap indexes are supported only on non-partitioned tables.

And with the 10g Database release, the concept of mapping a table is extended to support mapping tables that are equally partitioned with respect to the base table. This enables the creation of bitmap indexes on partitioned IOTs.

The rowids used in bitmap indexes on index-organized tables are in a mapping table, not in the base table. The mapping table maintains a mapping of logical rowids (needed to access the index-organized table) to physical rowids (needed by the bitmap index code). Each index-organized table has one mapping table, used by all the bitmap indexes created on that table.