Cause
The policy which was being dropped due to event propagation from OID was applied to some table or schema.
The policy which was being dropped due to event propagation from OID was applied to some table or schema.
Drop a policy in OID only if it is not used in any of the databases using the policy.
Try the following links for this error:
http://docs.oracle.com/cd/E16655_01/server.121/e26079/e12400.htm
https://community.oracle.com/message/9901698
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