To define an index for a relation using the DEFINE INDEX
    statement, you need the Oracle Rdb DEFINE privilege for the
    relation.

    When the DEFINE INDEX statement executes, Oracle Rdb adds the index
    definition to the physical database. If you have invoked the
    database with the PATHNAME specification, the definition is also
    added to the data dictionary.

    If you define a sorted index for a relation that contain no data,
    the root node for the index is not created until the first record
    is stored. When an RMU/VERIFY operation encounters a sorted index
    with no root node, it reports the index as empty.

    You must execute this statement in a read/write transaction. If
    you issue this statement when there is no active transaction,
    Oracle Rdb starts a read/write transaction implicitly.

    You cannot define a hashed index in a single-file database.

    If you define a hashed index, you must specify a storage map for
    it with the index-store-clause. The storage area that you specify
    must have a MIXED page format.

    An optional keyword that causes Oracle Rdb to create ascending
    or descending index segments. If you omit the ASCENDING or
    DESCENDING keywords, ASCENDING is the default. To sort records
    in a particular way in the result of a particular query, specify
    the sort order in the SORTED BY clause.

    Other users are allowed to be attached to the database when you
    issue the DEFINE INDEX statement.