Oracle/PLSQL: ORA-00023 Error

Error:

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

Cause:

You tried to detach a session but it contains references to the process memory (PGA) through any of: an open network connection, a very large context area, or operating system privileges.

Action:

The options to resolve this Oracle error are:

If the session has an open network connection or a very large context area, you can try closing the session's database links and cursors.
If the session has operating system privileges, you will not be able to detach the session.