The PCA Collector supports the following application program
    interface to user routines.

    pca-control-flag =
       entry-routine(
          ap-pointer,
          sequence-number,
          CPU-time,
          system-service-name-pointer,
          system-service-name-index,
          user-routine-buffer-pointer)

    pca-control-flag =
       exit-routine(
          ap-pointer,
          sequence-number,
          CPU-time,
          system-service-name-pointer,
          system-service-index,
          user-routine-buffer-pointer)

    Routine Parameter           Description

    pca-control-flag            Flag to indicate whether PCA is to
                                attempt to write the system service
                                record. The write will only be
                                attempted if the low bit is set.
    ap-pointer                  The contents of the argument pointer
                                at the system service call by value.
    sequence-number             The PCA sequence number corresponding
                                to the performance data record by
                                value.
    CPU-time                    The CPU time by value.
    system-service-name-        The name of the system service being
    pointer                     called by the address of a counted
                                ASCII string.
    system-service-index        The index of the system service being
                                called by value.
    user-routine-buffer-        User specified buffer by reference.
    pointer

    The following rule applies regarding the construction of user
    routines images:

    1. The user must write a shareable image, making the entry and
       exit routine names UNIVERSAL;