I've been asked to assemble a DBA team to support databases at our company. Previously we've only had one full time DBA but in the last two months I have begun transitioning a developer into the role, and have hired a Sr. DBA as well. I'm a fairly seasoned DBA but have never been a part of a DBA team and therefore I have some questions about how to assemble one.

Specifically: what kind of on-call rotations / schedules should I look at? Currently the sole DBA is pretty much 24x7 for everything, and it can be a strain. Soon she will have two other DBAs to support her, what kind of rotations should I consider? There are about twenty databases of varying visibility; should I establish primary and secondary DBAs for each instance, then establish a rotation appropriately? Or is it more effective for each DBA to be responsible for all instances, and simply establish a schedule a la "you are off-call every third week" in a staggered 2-on-1-off fashion?

I'd love to hear what you're using, what works and doesn't work. Any other thoughts on the formation of a DBA team (things to keep in mind) would be appreciated!