Hi Venga,
On doing a quick research on this it seems that your use case is NOT achievable by Siteminder configuration.
See the details below :
"Due to the Client-Server design and the HTTP stateless protocol, this is not possible unless the client and the server make a persistent connection.
Then the server will be able to send the alert to the client.
As the browser will establish a non-persistent connection to the webserver, the browser(client) should handle this situation.
In that sense, customer can achieve this by adding a custom code at the web content to monitor HTTP_SM_TIMETOEXPIRE header variable and compare it with the
current time then display the message.
This should not be SiteMinder functionality as a server will not establish a connection back to the browser to send an alert.
If customer wants to achieve this functionality, there are many ways to do it. For example, customer can use asp or jsp to have a frame and add a code to
calculate the time difference between HTTP_SM_TIMETOEXPIRE and the current time. If the difference becomes 2 minutes (or whatever configured value), customer can popup a message box to alert that the session will timeout.
13/7/2016: Please note, HTTP_SM_TIMETOEXPIRE stores only the Max Timeout Value. There is no other default header to store the IDLE time out value.
Hope the information helps.
Cheers,
Ujwol