non-substitutable resources?
 

I am planning a construction job. Most tasks require two or more people (e.g., because one person cannot lift something by himself). I have assigned several tasks to both A and B. A is taking vacation all of October. After I level resources, I see that OmniPlan has scheduled some of these tasks in October, assigning the work entirely to B and doubling the duration.

Instead, I want these A and B to cooperate on these tasks, each contributing half the total effort. No task should be scheduled for October. How can I make this happen?

One somewhat unorthodox way you might approach this is to send them both on vacation for that month :-)

Seriously, mark both A and B as unavailable for that month. Create another staff resource (C) to give assignments to for that month for the worker (B) who didn't go on vacation. If all the 2-person tasks are assigned to A+B, none of them should be leveled into the vacation month. You might have to do a bit of iteration to figure out how many/which tasks to assign to C to keep the schedule filled up in the vacation month. I'd be curious to know if this works...

I'm curious too, but not enough to bother to try your suggestion. I would not foist this solution on others, so I'll do what I always seem to do with scheduling programs: override the load leveling with constraints.

And I thought my suggestion was awkward :-)

It seems like what one would want for this sort of thing in general is the ability to assign to a group (already present) but instead of having OP just select one resource from the group, it somehow be marked as a task where all of the group members need to be assigned. I think this would be a property of the task, especially given that a resource can't be part of multiple groups. It would be useful for things like putting group meetings into a schedule, too.

I like your suggestion, but would prefer that it not be limited to pools (resource groups). The restriction that a person can be in only one pool, or outside of any pool, but not both, is quite severe. So far it's prevented me from using pools at all. So I would prefer to be able to assign one or more resources (including maybe a pool or two) to a task and then be given perhaps a check box that, which checked, forces full participation by all resources for the duration of that task.

When I am sharing a plan with others, awkward is not as bad as confusing. Besides, I no longer consider override of load leveling awkward, having been forced to do it with every scheduler I've use. Time constraints are better understood and easier to forecast than efficiencies of resources. Therefore constraints in time will always trump load leveling here and there, it seems to me, even with perfect software.

Yeah, looking back I should have distinguished between groups of resources (assign something to more than one resource) and actual OmniPlan resource groups as implemented today. There probably isn't any real need to restrict this functionality to actual OmniPlan resource groups; just assign all the resources you want and tick the box that says "keep 'em all busy!" :-)