While Additive strategies are clear, I have a problem understanding the Alternative strategy for resource allocation and how it related to the value of Required Employees.
For example, a simulation with two activities having the same processing time, requiring the same number of employees but with respectively Additive and Alternative strategy, produces exactly the same behavior in ARIS. The only way I can explain this so far, is that the value of Required Employees is ignored when the allocation is set to Alternative and always assumed as 1. However, there is no hint about that in the simulation documentation (Help and training materials).
If that is the case anyway, then how to simulate the following situation:
An activity should be started as long as one of the required resources is free but is of such a type, that a second resource, if available, can shorten the time it takes to complete a simulation folder. That means that the activity can takefor example 1 hour, if both are available, 2 hours if only one, and between 1 and 2, depending when the second would join, and of course more than two, if there is not even one available when the folder arrives.
The allocation strategy is only relevant in cases where multiple resource objects(!) are attached to a function. For example if you attach two organizational unit objects to a function and both are attached with a 'carries out' connection, then only one of these two is needed and used for carrying out the function (alternative strategy). If at least one is attached with a 'contributes to' connection, then both are needed and used for carrying out the function (additive strategy).
I don't think that allocation strategies are relevant for your simulation problem. The desired behavior could likely be achieved by detailing the function with an AND block that contains two functions which can be carried out in parallel. The same resource object should be attached to both functions and its number of employees should be 2. If none of the employees is available, no function can be carried out. If one employee is available the functions are executed sequentially. If both employees are available, the functions are carried out in parallel.