You have deployed applications that use client JARs in Application Server 8.x. You upgrade your existing installation to Application Server 9.1 Update 1. You could run into problems while trying to run these applications (that were deployed in Application Server 8.x) in Application Server 9.1 Update 1.
To solve this problem, perform the following steps:
After upgrade, start Application Server 9.1 Update 1.
Use the asadmin get-client-stubs command to transfer the missing client stubs to a local directory. See get-client-stubs(1).
Run the appclient pointing to the client JAR files in the local directory.