No, using the same soap-action is not possible. Uniqueness is enforced by TIBCO ActiveMatrix (AMX), as mentioned in the Composite development documentation in the SOAP Binding Flags section. The specifications are unclear with regard to uniqueness of soap-action for _each_ operation. They indicate that it should be unique but it is not explicitly stated.

The reason for the enforcement of soap-action uniqueness for each operation within AMX is to avoid the situation where two or more operations have the same input message definition. In this case, the HTTP message for the operations would be identical as they have the same  soap-action.

Some type of proxy could be used but it should not be between the soap binding and the mediation component because the mediation component does not use the  soap-action and operation dispatch is done within the SOAP binding.

Example:

  Client (sends SOAP message with empty or shared  soap-action header)

    --> Proxy (Intercepts the SOAP message and adds the proper  soap-action header)

    --> AMX Composite (Each operation has its own  soap-action)

Any programming language implementation, including TIBCO ActiveMatrix BusinessWorks, could be used to accomplish this.