OCI-00951
cluster not empty
Cause
A DROP CLUSTER statement specified a cluster that was not empty. A cluster may not be dropped if it contains any tables, unless the optional INCLUDING TABLES clause was specified. Tables may also be removed from a cluster by using the DROP TABLE command.
Action
Either specify the INCLUDING TABLES clause in the DROP CLUSTER statement or remove all tables from the cluster with the DROP TABLE command before issuing the DROP CLUSTER command.