Load Testing an Outsystems APP

Load Testing an Outsystems APP

Hi all,

I am making load tests to an outsystems app using QTest, a tool from Quotium. This tool captures, in a script, the HTTP traffic (get's, post's, and their responses) between the client browser (IE in our case) and the Server of an user interaction (test scenario). Then, one must parametrize all the are variables (such as session id's, input data, etc.), and the tool can reproduce the scenario for severall users.
The tests are developed by a separated team than the development. And we have no access to the code, nor to the development proccess at all, as this is suposed to be completely independent, such as in an audit fashion...
We already did some scenarios and reproduced them with success! However we got a scenario where we find the "SessionState" variable. This variable comes from the server and we have no problem parametrizing that. The problem is that almost requests that uses this "SessionState" variable, also use a variable called "_" (without the quotes). For instance:

As state above, the SessionState variable comes from a previous response from the Server, so we have no problem paramtrizeing it. The problem is with "_" variable which we don't know how to parametrize, as the value that is sent is not found on any response from server.
When we reproduce the script with all variables parametrized (except for the "_" variable) we got an "Internal Error" from the Server on the first request that uses the "_" variable, so we really think that's the problem.

Does anyone know how to solve this? Shall this parameter be generated by a javascript function that cames from the Server?
Any clue?

Thanks all in advance!!