A select function is processing an IUCV interrupt. If the interrupt indicates a message complete from TCPIP, IUCV merges the AF_IUCV file descriptor sets with the AF_INET file descriptor sets returned by TCPIP. If there are AF_IUCV descriptors in the caller's masks, any IUCV interrupt selected by the caller's mask completes the request and the caller's mask is set accordingly. If an AF_IUCV interrupt is received for a descriptor not in the caller's mask, the select function continues waiting. This message is generated only when socket tracing is in effect.