ORA-13759: User string cannot remove reference string .
Cause: The user attempted to remove a SQL Tuning Set reference that does not exist. The user might not own the reference.
Action: Check the reference ID and the reference owner and retry the operation.
Cause: The user attempted to remove a SQL Tuning Set reference that does not exist. The user might not own the reference.
Action: Check the reference ID and the reference owner and retry the operation.
