In addition to the above REXX client interface, several facilities provide support for the use of application servers written in REXX. One of these facilities is the WAITREQ command, which is used by servers to wait for requests from clients. Another facility, the C2S and S2C commands, provide the ability for servers to fetch or set the contents of client variables. Another capability, Automatic Server Initiation (ASI) provides for servers to be started automatically when a request arrives from a client.