@SourabhSaha,
Are you working with a trial edition of Blue Prism? If the license you have limits you to no more than 1 concurrent session I imagine that is the case.
@John Carter has made some good points above, and the Web Services User Guide he's directed you to includes some valuable information regarding sessions and run-modes.
In your case, if you were to set both Object A and Object B to have a run-mode of
Background what I envision happening here is that a new session would be created for each object. When Object B attempts to the start the specific process (pulled from the queue) that would result in another session being created - assuming this process also has a run-mode of
Background or
Foreground. If the run-mode is
Exclusive it will terminate with an error.
Given the restriction on your license, this will not work. Something to understand about auto-initialization is that Blue Prism will not terminate the sessions tied to objects A or B immediately. You may only make a single call to say Object A, but the session will continue to live on for a period of time after that call completes. Eventually, Blue Prism will determine that there have been no new calls to that object and terminate the session. With manual-initialization you could actually control when the session is terminated. However, this still wouldn't work for you because Object B would still be running as it tries to start the process, so at a minimum you would need a license that supports at least 2 concurrent sessions.
Cheers,
Eric