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Standard (B-tree) and Bitmap

A standard, B-tree index contains an entry for each value in the index key along with disk address of the row whcre the value is stored. A B-tree index is the default and most common type of indcx in an Oracle database.

A bitmap index uses strings of bits to encapsulate values and potcntial row addresses. It is morę compact than a B-tree index and can perform some types of retrieval morę efficiently. For generał use, however, a bitmap index requires morę overhead during row operations on the table and should be used primarily for data warehouse environments, as dcscribed in Oracle Database Data Warehousing Guide.