1. A shared resource system comprising: a plurality of client computers; a plurality of provider computers selectively making resource capacity available to said plurality of client computers; a network connecting said plurality of client computers to said at least one provider computer, said plurality of client computers and said plurality of provider computers passing messages to each other over said network, wherein said messages include request messages from requesting client computers requesting resource capacity from said plurality of client computers and confirmation messages confirming resource availability and/or allocation; and two or more of said plurality of client computers requesting resource capacity from said plurality of provider computers, said plurality of provider computers further sending confirmation qualification messages notifying in real time each of said two or more of any potential conflicts with any portion of the requested capacity as each conflict arises, the qualification messages indicating the size of the portion of requested resources in conflict, such that each notified requesting client computer can modify respective resource requests responsive to said qualification messages to eliminate resource conflicts prior to returning a commit message to said plurality of provider computers, wherein said messages further include commit messages from requesting client computers, each requesting client computer sending a commit message responsive to unqualified confirmation messages, and selectively sending a modified request message or cancellation message responsive to qualification messages, modified request messages comprising requesting other resources from a selected provider, and selecting another provider to provide requested capacity.