How to control running concurrent program programatically

You can use
Fnd_Conc_Global.set_req_globals
e.g) for pausing the running conc process

use this in package which you want to pause.
Fnd_Conc_Global.set_req_globals (conc_status => 'PAUSED'
,request_data => 'QUERY' --This is to pass some parameters to the package when pausing) ;

To run the resume the process again,call the same so now it starts running

Fnd_Conc_Global.set_req_globals (conc_status => 'PAUSED'
,request_data => 'QUERY');