The Transaction block performs transactions on multiple items at the same time. The block takes in all available items (up to a specified maximum capacity) and performs a transaction (see below). The items exit one at a time.
This block can also be used as a simple operation on one item at a time. To do this, set the maximum number of transactions to 1 and specify a transaction time in the dialog.
The transaction can be:
• A movement from one block to another with a transaction or processing time. In this case, each item entering will be delayed for the specified amount of time. The time is set in the dialog or dynamically through the D input connector. The item with the shortest total time in the block (considering arrival time and transaction time) will exit first. For example, if the block takes in three items 1 time unit apart and the transaction time is the same for each item, the first item arriving will exit first. However, if the transaction time is 10 for the first two items, but 1 for the third item, the third item will exit first. It is strongly recommended that you preceed and follow this block with a queue-type block such as a Stack or Repository to hold items waiting to be transacted and to hold items that have been transacted.
• A movement from one block to another, with zero (0) transaction time. In this case, the block just moves items from one point to another with no delay. You would use this feature to show items being sent from one block to another where the delay is insignificant, such as multiple pieces of mail being transmitted electronically.
Dialog Choices:
Arrivals/Departures: Displays the number of items received and released by the block.
Maximum number of transactions: The maximum number of items that can be transacted at any time.
Strip attributes from incoming items: When checked, will remove all attributes associated with incoming items. This option should be used with caution, since attributes that have been removed cannot be recovered.
Transaction time: The amount of time that a transaction requires in simulation time units. This is overridden by the value from the D input connector if it is connected. The time can be 0 (for no delay) or any number larger than zero.
Utilization: Displays the utilization rate. A utilization of 1 indicates the Transaction is fully utilized; the idle time rate is 1 minus the utilization rate. This shows the ratio of time that items are busy, based on the maximum number of transactions specified in the dialog. For example, if the maximum number is set to 5, and the block processes 2 items 100% of the time, the utilization is .40 (40%).
Connectors:
The item input takes in items to be transacted.
The item output is the items released to the model one at a time.
D: The delay or processing time. This is used to dynamically set the transaction time.
#: The current number being transacted.
u: Utilization. Note that the calculation is based on the maximum number of items entered in the dialog.
Animation:
Green circles show items entering and exiting the block. Text on the icon shows the number of items being transacted.
