In a sysplex, software maintenance and software upgrades are typically applied in a "rolling" fashion, with new software being installed on one system at a time. It might take weeks or months for the change to be fully deployed throughout the sysplex. In the mean time, installations expect applications to remain available and operational. Thus different levels of clients, servers, or both can be running simultaneously in the sysplex, perhaps even within the same system. Clients might require their requests to be processed either by servers running at certain levels or by servers that support certain features. A given server might be able to offer different kinds of response data depending on what the client understands. Some levels of a client might be incompatible with some levels of a server.