PIOPAGES specifies the size of the process I/O segment, which
    holds data structures and buffer pool space for RMS to use
    when it handles I/O that involves process-permanent files. Once
    PIOPAGES is reset in SYSGEN, any new process receives the changed
    value.

    This special parameter is used by VSI and is subject to change. Do
    not change this parameter unless VSI recommends that you do so.

    PIOPAGES is an AUTOGEN and DYNAMIC parameter.