Sharing effort between Effort on Allocation modelled resources

If you use the Effort on Allocation modelling type - useful when you know the amount of effort that is required to complete a task - and more than one permanent resource is going to work on the activity and the resources' effort can be defined by the duration of the task (ie where Duration is the calculated parameter), you can specify that the effort is shared between the resources at the point at which the resources are assigned to the task.

For example, you might have a task that you know will take 4 days worth of effort to complete and two resources who can carry out the task by working together, both with an allocation of 0.5. Modelling the resources to use the Effort on Allocation modelling type and configuring them to share the effort means that:

When the first resource is assigned to the task, the effort of the allocation is defined by the duration of the task. As the resource has an allocation of 0.5 and the task duration is 4d, the allocation's effort is assumed to be 4d and the duration of the allocation - and the task - is extended to 8d. (If the resource was not configured to share the effort, the allocation's effort in this instance would be set to 2d and the duration of the allocation would be 4d.)
When the second resource is assigned to the task (this also applies to any subsequent allocations), the remaining effort of any existing shared effort allocations is summed up and redistributed between all of the shared effort allocations. In this example, the 4d effort on the first allocation is redistributed between both allocations, so both are given 2d of effort. (If the resources were not configured to share the effort, the second allocation's effort would be 2d and the duration would be 4d.)
If the first allocation had already reported 1d of effort, the remaining 3d of effort would be shared between the two allocations when the second resource was assigned. (If the resources were not configured to share the effort, the remaining 3d of effort would remain on the first allocation.)

Unless you make any further 'share effort' allocations to the task, the resource allocations behave in exactly the same way as Effort on Allocation resource allocations that are not configured to share effort: the only difference in behaviour is at the point at which resources are allocated to tasks.

To configure an Effort on Allocation modelled resource to share effort, select the Share effort check box on the Assignment tab of the Permanent Resource Properties dialog. You can also configure individual Effort on Allocation modelled resource allocations to share effort by selecting the Share effort check box on the Details tab of the Permanent Allocation Properties dialog. Note that configuring Effort on Allocation modelled resources to share effort only affects new assignments. Selecting this check box for existing allocations will not redistribute their effort, unless further 'share effort' resources are assigned subsequently to the task.

Sharing effort between Effort on Allocation modelled resources in this way is similar in some ways to using the Effort Activity Budget modelling type, but differs from it in the following ways:

The effort budget of tasks is ignored; the effort of the allocations is defined by the duration of the task when the first resource is assigned to it.
The remaining effort is redistributed between allocations only when a new 'share effort' resource is assigned to the task.