Let's say you have 1000 users and want to break it down by half. Say from A to M and N through Z. You can set up two separate instances as follows:
Who "Blank" to M? Because numbers sort BEFORE "A" so things beginning with numbers are lost if you do not do "Blank" as your start.
Then "N" to "Z":
Just to be safe I'd run each of these on separate machines, but you use the SAME mapping tables for each.
Oh -- and if you want to insert just ONE calendar to test, this is the way to do it:
Put the same name in each endpoint box.
And this is an Oracle Calendar to Office 365 migration in action: