Usually due to a bad (or non-existent) background process image.
Get a good background process image.
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Try the following links for this error:
http://docs.oracle.com/cd/E16655_01/server.121/e26079/e0.htm
https://community.oracle.com/message/9657468
https://community.oracle.com/message/9156434
https://community.oracle.com/message/9160014
https://community.oracle.com/message/10600979
https://community.oracle.com/message/1941387
https://community.oracle.com/message/2812180
https://community.oracle.com/message/10781204
https://community.oracle.com/message/2176557
https://community.oracle.com/message/1984714
https://community.oracle.com/message/9140333
https://community.oracle.com/message/2839715
https://community.oracle.com/message/3988952
https://community.oracle.com/message/2445649
https://community.oracle.com/message/1983590
https://community.oracle.com/message/9301192