1. A system for managing a plurality of database systems, comprising: (a) a domain comprised of a plurality of database systems, wherein each of the database systems performs database queries to retrieve data stored by the database systems; (b) one or more virtual regulators, performed by one or more processors, for managing the domain; and (c) one or more closed-loop system management (CLSM) regulators, performed by one or more processors, for managing each of the database systems in the domain; (d) wherein both the virtual regulators and CLSM regulators perform parallel virtual optimization of the database queries performed by the database systems; (e) wherein the virtual regulators and CLSM regulators include proxy query optimizers that emulate a query optimizer function found in the database systems; (f) wherein the proxy query optimizers in the virtual regulators and CLSM regulators execute in parallel, and each of the proxy query optimizers is assigned a different portion of a query execution plan space to explore; and (g) wherein each proxy query optimizer explores its portion of the query execution plan space and upon completion of its analysis or expiration of a specified resource or time period, submits its best query execution plan to its superordinate proxy query optimizer for comparison with the query execution plans submitted by other proxy query optimizers, in order that the best query execution plan identified by all of the proxy query optimizers is communicated to the proxy query optimizer of the virtual regulator.