The list of steps depend on how is your current application built (e.g. are you using direct global access vs. SQL). Depending on which direction you want to go you could simply wrap your existing objectscript code in either stored procs or services and access them from Java or rewrite all your existing logic in Java.

Again, the steps would depend on what exactly you're trying to accomplish and your current app makings.

It's hard to tell what's wrong without all (or more) details. Are you getting an error? If you're not getting an error, are you passing the correct values (values that should return records)? Also, have you tried creating a very basic stored proc in Oracle (select current_date from dual or something like that) and try to use that from IRIS? The exercise will help you eliminate variables for possible issues.

To add a new header, you need to create a subclass of %SOAP.Header with the property you need. Once you have that then you can add it to the appropriate array e.g.

S myheader = ##class(MyNewHeader).%New()

S myheader.mykeyproperty = <myvalue>

D myservice.HeadersOut.SetAt(myheader,"MyNewHeader")

This is assuming the header is not automatically generated from the XML schema.