If you do not specify storage-spec in a CREATE INDEX statement, the indexes are fragmented the same as the underlying table, subject to all the restrictions on fragmented indexes. For example, an error is returned if the underlying fragmentation strategy is round-robin, and the index is unique. You cannot alter this type of index fragmentation. If you want to change the index fragmentation, use the INIT option of ALTER INDEX to detach the index. That operation makes the index and table independent and lets you alter each independently.