The MQSeries interface can have as many requests 'active' at any point in time as the number of licensed ITP/Document Processors. Provided that all ITP/Document Processors are running, this ensures that as many requests as possible are handled concurrently. If less are running, some of the 'active' MQSeries jobs will be queued at ITP/Server for processing. The latter has consequences for the MQSeries priority mechanism (refer to below), so we advise to always start all available ITP/Document Processors (there is no reason not to).