Handling Multivolume Files
The Connect:Direct® for z/OS® mount message is issued only for the first volume of a file, when a multivolume file is requested. Subsequent mount requests causes a SYSZTIOT enqueue during end-of-volume processing.
To keep IBM® Connect:Direct from long waits while a second or subsequent volume is mounted, use UNIT=(unit,P) or UNIT=(unit,n) for the UNIT keyword of the COPY statement.