Programming Interface Information: This information is NOT intended to be used as Programming Interfaces of z/VM.

#### VIUBK

Prolog

Control Block Contents
VIUBK DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### VIUBK Prolog

     NAME       : HCPVIUBK
     DESCRIPTION: VDEV I/O Assist Utilization Block
     DSECT      : VIUBK
     FUNCTION   : To track a device's utilization of I/O Assist
     LOCATED BY : VDEVIUBK Field of VDEV - Virtual Device Control Block
     CREATED BY : VIUBK's are dynamically created by HCPIAXBL for I/O
                  Assist eligible devices when we log on, attach a
                  device, redefine a device (if VIUBK did not already
                  exist).
     DELETED BY : VIUBK's are deleted by HCPIAXBL when a redefine makes
                  a device ineligible, or by HCPVDBDL when it deletes the
                  associated VDEV.
     SERIALIZED : The VDEVLOCK should be held when referencing VIUBK fields.
     NOTES      :
         - When the VIUBK is first built, VIUCNTOT is
           incremented.
         - A transition from IN to OUT is considered to pass
           through a LEAVING state, but to spend no time there.
         - (Therefore) The counters VIUCNTOT, VIUCNTIN and
           VIUCNTLV will all be within one of each other.  The
           state of the device could be determined from these
           counters - When CNTOT is one greater than the other
           two, the device should be in the OUT state.  When
           CNTLV is one less than the other two, the device
           should be in the IN state.  When they are all equal,
           the device should be in the LEAVING state.  If this
           is not true, this should be considered an error in
           the code maintaining the counters.

#### VIUBK Control Block Content

#### VIUBK DSECT

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      VIUBK          VDEV I/O Assist Utilization Block
    0000    0 Dbl-Word     8 VIUSTAMP       Timestamp of last I/O Assist
                                            transition
    0008    8 Bitstring    1 VIUSTATE       Describes the device state NOTES
                                            : This state field is for
                                            statistical purposes and NOTES :
                                            should not be used to determine
                                            the state of the NOTES : device
                                            by CP code.
              00000000       VIUISOUT       0 Device is out of I/O Assist
              00000001       VIUISIN        1 Device is in I/O Assist
              00000002       VIULEAV        2 Device is LEAVING I/O Assist
    0009    9 Bitstring    1 * (3)          RESERVED FOR FUTURE IBM USE
    000C   12 Signed       4 VIUCNTIN       Count of transitions in I/O
                                            Assist
    0010   16 Signed       4 VIUTIMIN       Total time spent in I/O Assist
                                            (in micro seconds)
    0014   20 Signed       4 VIUCNTLV       Count of transitions leaving I/O
                                            I/O Assist
    0018   24 Signed       4 VIUTIMLV       Total time spent leaving I/O
                                            Assist (in micro seconds)
    001C   28 Signed       4 VIUCNTOT       Count of transitions out of I/O
                                            Assist
    0020   32 Signed       4 VIUTIMOT       Total time spent out of I/O
                                            Assist (in micro seconds)
    0024   36 Signed       4 *              RESERVED FOR FUTURE IBM USE
              00000005       VIUSIZE        (*-VIUBK+7)/8

#### VIUBK Storage Layout

    *** VIUBK - VDEV I/O Assist Utilization Block
    *
    *     +-------------------------------------------------------+
    *   0 |                       VIUSTAMP                        |
    *     +------+--------------------+---------------------------+
    *   8 |:STATE|////////////////////|         VIUCNTIN          |
    *     +------+--------------------+---------------------------+
    *  10 |         VIUTIMIN          |         VIUCNTLV          |
    *     +---------------------------+---------------------------+
    *  18 |         VIUTIMLV          |         VIUCNTOT          |
    *     +---------------------------+---------------------------+
    *  20 |         VIUTIMOT          |///////////////////////////|
    *     +---------------------------+---------------------------+
    *  28
    *
    *** VIUBK - VDEV I/O Assist Utilization Block

#### VIUBK Cross Reference

    Symbol         Dspl Value
    -------------- ---- -----
    VIUCNTIN       000C
    VIUCNTLV       0014
    VIUCNTOT       001C
    VIUISIN        0008 00000001
    VIUISOUT       0008 00000000
    VIULEAV        0008 00000002
    VIUSIZE        0024 00000005
    VIUSTAMP       0000
    VIUSTATE       0008
    VIUTIMIN       0010
    VIUTIMLV       0018
    VIUTIMOT       0020

This information is based on z/VM V5R2.0. Last updated on 12 Apr 2006 at 17:37:56 EDT.
Copyright IBM Corporation, 1990, 2005