When starting the WebSphere Portal server, you see SRVE0203E and SRVE0206E errors for the com.ibm.wps.engine.Servlet indicating that required classes are missing.
The root error is:
[1/3/13 16:44:35:116 EST] 00000037 extension W
createServletWrapper Servlet portal is currently unavailable:
SRVE0203E: Servlet [portal]: com.ibm.wps.engine.Servlet was found, but
is missing another required class.
SRVE0206E: This error typically implies that the servlet was originally
compiled with classes which cannot be located by the server.
This error can be caused when classes are missing or inaccessible from the PortalServer/shared/ext directory.
The PortalServer/shared/ext directory should contain a jar file called "shared.ext.jar". The META-INF/MANIFEST.MF within this jar file contains a list of other jar files throughout the Portal file structure. If the shared.ext.jar file or any of the jar files referenced in the MANIFEST.MF file are missing, this error will occur.
Resolving the problem
Check to see if PortalServer/shared/ext/shared.ext.jar exists. If it does, check the MANIFEST.MF file within the shared.ext.jar to get a complete list of jar files loaded by Portal. Check for the existence of each of those jar files.
If any are missing, they can be copied from another Portal server that is at the same maintenance level. If you do not have another Portal system available, contact IBM support.