The SET IO_SERVICES command enables the collection of I/O system
    services data. After you enter the GO command with I/O data
    collection enabled, the Collector intercepts every I/O system
    service call during program execution. For each such call,
    the Collector gathers the appropriate information from the
    File Access Block (FAB), Record Access Block (RAB), or other
    parameters and records it in the performance data file. The exact
    information gathered depends on the I/O service, but will include
    the program address of the call, the name of the service, the CPU
    time stamp. It may also include the name of the file accessed,
    the record size of the transfer, the physical I/O read and write
    counts, and other information.

    You must collect stack PC information if you want to use a /MAIN_
    IMAGE, /CUMULATIVE or /STACK_DEPTH qualifier with the PLOT or
    TABULATE command in the Analyzer.