For managing a pool of virtual computer systems, master status and a rebasing task are assigned to at least one virtual computer system of the pool. A non-reserved status is assigned to virtual computer systems of the pool that are not assigned tasks. A virtual computer system of the pool is selected to respond to a rebasing request. The selecting includes selecting one of the at least one virtual computer system that currently has a master status and that currently has a processing load less than a predetermined threshold and, when no virtual computer system of the pool currently has a master status and a processing load less than the predetermined threshold, selecting a non-reserved one of the virtual computer systems to perform rebasing for the request and changing the non-reserved status of the selected, non-reserved one of the virtual computer systems to master status.