After the resource entities have been allocated to a controlling entity (or in the case of a Batch block, a carrier entity), the controlling entity usually continues to flow through the model. In the banking system example, the controlling entity might move on to a Delay block for a period of time and then be routed to a Release block to have the resource entity deallocated. However, if you are modeling a more complicated system, it is possible that resource entities stay with a controlling entity as it flows through various parts of the model. For example, in an emergency room simulation, a patient entity entering the emergency room might require a nurse, a doctor, and a surgery room simultaneously. After the required resources are seized, then the patient entity goes to a Delay block that represents the surgery. After surgery, the doctor and surgery room resource entities might be released from the patient. However, the nurse entity might stay with the patient entity and a recovery room resource entity might be added.
In a manufacturing example, parts could be modeled as resource entities, and they could be continually added to the controlling entity as it progresses down a virtual assembly line. In this case, the controlling entity never releases the part entities because they are essentially consumed to build the final product.