operation requires database is in EXCLUSIVE mode

Try the following links for this error:

http://docs.oracle.com/cd/E16655_01/server.121/e26079/e12700.htm

https://community.oracle.com/message/10977513

https://community.oracle.com/message/1701273

https://community.oracle.com/message/4239555

https://community.oracle.com/message/3704620

https://community.oracle.com/message/2538597

https://community.oracle.com/message/3167756

https://community.oracle.com/message/1391546

https://community.oracle.com/message/946074

https://community.oracle.com/message/1324306

https://community.oracle.com/message/1592972

https://community.oracle.com/message/2022617

https://community.oracle.com/message/613162

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