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Resources and Shifts 231
Scheduling resources
• UseShiftblockstocontrolaspectsofoneormoreresourceblocks.Thisisdiscussedin “Resources model” on page 235.
Using the TR (Total resources) connectors
Blocks that provide resources (whether as items or as resource pool constraints on items) have value connectors labeled TR (total resources). You use the TR input connector to change the total number of resources available. This change can be scheduled, such as when workers take breaks, or unscheduled, such as an equipment failure.
The value at the TR connector determines how many resources the block has and can result in an increase or a decrease in resource availability. For example, if the initial number in a Resource Item block is 10, and the block gets a value of 3 at its TR input connector, the block will eliminate 7 resources from its availability list. If the block doesn't have enough resources to dispose at the time of the change, it will dispose of them as they return.
Scheduling Resources model
It is common to schedule the avail- ability of resources based on some factor in the model, typically time. For example, in the model dis- cussed in “Scheduling activities” on page 187, you could have scheduled workers in the diner depending on the time of day using the Resource Item and Create blocks.
The new model is shown at right. It assumes there are three workers ini- tially available when the coffee shop opens at 6am. Two additional workers arrive after 5 hours and remain just for the lunch period, from 11am to 2pm (1400 hours). The coffee shop closes after 10 hours.
Scheduling Resources model
Discrete Event

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