An attempt was made to use the DROP INDEX ONLINE, ALTER TABLE DROP CONSTRAINT ONLINE, or ALTER TABLE SET UNUSED COLUMN ONLINE statement on an table type (for example, cluster, temporary, index-organized table (IOT), external tables) that was not allowed.
Using the ALTER INDEX UNUSABLE ONLINE statement on certain types of indexes (for example, indexed-organized table (IOT), cluster, LOB, domain indexes) is illegal. Remove the ONLINE keyword from the statement.
Try the following links for this error:
http://docs.oracle.com/cd/E16655_01/server.121/e26079/e12700.htm
https://community.oracle.com/message/4491026
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