I am trying to change my Oracle password but get ERROR: ORA-00600
<p>My password has expired and when I enter a new one I get the following error and my password is not changed.  What is going wrong here?</p>

<p>ERROR:
ORA-00600: internal error code, arguments: [kpdbModAdminPasswdInRoot: not CDB],
[], [], [], [], [], [], [], [], [], [], []</p>

<p>EDIT:
Oracle personal edition 12c.
I am changing the password through the SQLPlus dialogue.</p>