18.ORA-00023: session references process private memory; cannot detach session

ORA-00023: session references process 

private memory; cannot detach session

Cause: An attempt was made to detach the current session when it contains references to process private memory.

Action: A session may contain references to process memory (PGA) if it has an open network connection, a very large context area, or operating system privileges. To allow the detach, it may be necessary to close the session's database links and/or cursors. Detaching a session with operating system privileges is always disallowed.