Before upgrading to Weblogic 12.1.2 there is one question: Is it possible that WLS 12.1.2 web services can communicate with WLS 8.1 clients or do we have to roll out new client jars to all our customers?
The WebLogic Server 8.1 Web services stack has been removed in the WebLogic Server 12.1.1 release. Therefore, WebLogic Server 8.1 Web services applications will no longer work. Oracle recommends that you upgrade such applications to the WebLogic JAX-RPC or JAX-WS stacks, per the instructions in "Upgrading an 8.1 WebLogic Web Service to 12.1.x".
The same applies to client apps as well. We recommend you to upgrade and roll out new client jars to access the services.