1. A method of applying an activation policy to a managed resource in a distributed computer environment, the method comprising: in a first resource manager that manages the managed resource, receiving status information associated with an externally-managed resource that is managed externally to the first resource manager by a second resource manager implemented at a different level of software in the distributed computer environment from the first resource manager, wherein the activation policy is associated with the externally-managed resource and is configured to make activation decisions about the managed resource based upon a status of the externally-managed resource; and in the first resource manager, applying the activation policy to the managed resource using the status information; wherein the distributed computer environment includes a plurality of computers, wherein the managed resource includes a resource instance resident on each of the plurality of computers, wherein the status information identifies a computer among the plurality of computers upon which the externally-managed resource is active, and wherein the activation policy is configured to activate a single instance of the managed resource that is collocated on the same computer as the externally-managed resource.