Batch processing allows you process/ship orders automatically in a batch. However you may want to restrict this operation based on some conditions. Such conditions can be whether you have sufficient stock and order is paid. To achieve this you need to create batch pilot (see documentation on how to create batch pilots), add Process Order step to the pilot and then set the conditions Order Paid and Only Sufficient Stock to Enabled and Cause Error. Then use this batch pilot to batch process orders instead of Batch Process Orders.