You can modify your Report Service settings from within Cognos Connection while logged in as an Administrator user.
Cognos Connection / Tools / Server Administration / select Report Service / properties / settings
Maximum number processes for the Interactive report service
2 For each server: 2 * # of CPUs
This setting dictates the number of BIBus processes that will be spawned to handle interactive processing activity. This must be considered in combination with the Batch Report service settings. An overlap in interactive and scheduled activity may require a lowering of this threshold to accommodate both processing activities.