Upgrade to 18c is Failing With ORA-29521: referenced name oracle/xdb/XMLType could not be found

• Errors during upgrade to 18c:
  • ORA-29521: referenced name oracle/xdb/XMLType could not be found
  • You may also see errors similar to ORA-29532: Java call terminated by uncaught Java exception: oracle.aurora.server.tools.loadjava.ToolsError:Error during loadjava: Failures occurred during processing.
• XDK is not installed prior to the upgrade

CHANGES

CAUSE

•  This is caused by unpublished <Bug 27916323 – XML COMPONENT NEEDS TO UPDATE UPGRADE/DOWNGRADE SCRIPTS FOR VERSION 18c>

SOLUTION

• If you have XDK installed prior to the upgrade to 18c, this error will not take place.
  • Install XDK 10.2 or Later.
  • It should be noted that a full JVM install will install XDK which can be accomplished using  Safe repair/reinstall of the JVM Component in 11.2 and up>

OR

• Apply <Patch 27916323 – XML COMPONENT NEEDS TO UPDATE UPGRADE/DOWNGRADE SCRIPTS FOR VERSION 18c>. If the patch is not available for your platform please log a support with the XML DB(XDB) team with your list of your one patches (opatch lsinventory -detail >inventory.txt).