EditingHoldModules < OpsRes

---+ Editing Hold Modules

_Hold_ modules belong to the _Advanced Process_ template (if you cannot find this template you may need to [[AttachArenaTemplate][attach it]]). After you have added a _Hold_ module by dragging it onto the flowchart view, you can edit it by double clicking. You can change the _Name_ of course, but the main functionality is determined by the _Type_. There are 3 types of _Hold_ module and we will discuss each one of them separately.

---++ Wait for Signal

This _Hold_ module stores entities in a queue until a unique signal is recieved during the simulation. Each time the signal is received a specified number of entities (defined by _Limit_) will leave the _Hold_ module queue.

Consider the example of simulating cars queing at a parking building exit while waiting for their prepaid parking tickets to be approved. The cars ( _entities_) must wait for the signal 10 to be sent in the simulation. When this signal is sent, one car (as defined by _Limit_) will proceed through the exit.

<img width="320" alt="Hold_for_signal.PNG" src="%ATTACHURL%/Hold_for_signal.PNG" height="263" />
---++ Scan for Condition

This _Hold_ module stores entities in a queue until a condition is satisfied. However, the _Hold_ module ONLY checks this condition WHEN A CALENDAR EVENT OCCURS. If the condition is true then the first entity in the queue may leave the _Hold_ module. This generates a new event and the condition is checked again. Each time the condition is true an entity leaves the _Hold_ module queue.

Below is an example of a _Scan for Condition Hold_ module from the case study: [[CourierServiceModel][Courier Service Model]]. As long as =LoadingInnerCity= is equal to one entities will leave the _Hold_ module.

<img width="320" alt="Hold_Scan_for_Condition.PNG" src="%ATTACHURL%/Hold_Scan_for_Condition.PNG" height="263" />
---++ Infinite Hold

This _Hold_ module stores entities in a queue for an infinite duration while the simulation is running.

*NB:* An infinite hold is usually combined with a _Search_ module and a _Remove_ module (See Arena help for more details).

Consider the example of simulating an emergency waiting room. Incoming patients (entities) are placed into a queue based on their Patient Type. Patient Type is an attribute assigned to each entity earlier in the model. Patients will wait in the Emergency Room _Hold_ module in queue until they are removed from the queue by an nurse (entity) at a _Remove_ module.

<img width="320" alt="hold_infinite.PNG" src="%ATTACHURL%/hold_infinite.PNG" height="263" />

-- Main.MichaelOSullivan - 25 Aug 2009
This topic: OpsRes > WebHome > ArenaGuide > EditingHoldModules
Topic revision: r9 - 2010-02-15 - KatTrevor