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

EXPBK

Prolog  

Control Block Contents  
   EXPBK DSECT
   EXPQUENT DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  


EXPBK Prolog

 NAME       : HCPEXPBK
 DESCRIPTION: EXPOSURE BLOCK
 DSECT      : EXPBK
 FUNCTION   : The exposure block contains necessary information
              about a CP volume for paging information.
 LOCATED BY : CPVEXPBK - For single exposure devices, points to
              the exposure block.
              For multiple exposure devices, points to
              the first one of a contiguous group.
 CREATED BY : HCPRDAAT - When the CP owned volume is brought on
              line at IPL time and during the ATTACH
              command processing.
 DELETED BY : HCPRDADT - When the CP owned volume is DETACHed from
              the system.
 SERIALIZED : EXPLCKFG - A Test and Set instruction is used to set
              the lock flag on to serialize this control
              block and the IORBK control block for the
              exposure.
 COMMENTS   :
              Each logical path to a device is an exposure.
              One device may have several exposures.  If so,
              each exposure has its own EXPBK, and all the EXPBKs
              for a single device are located in contiguous
              storage.

 

EXPBK Control Block Content


EXPBK DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      EXPBK          EXPOSURE BLOCK
     Flags for the exposure block.
0000    0 Signed       4 EXPFLAGS (0)   Flags for the exposure block
0000    0 Bitstring    1 EXPLCKFG       Exposure lock byte. X'FF' -
                                        Indicates this exposure is
                                        locked. X'00' - Indicates this
                                        exposure is available for use
          .... ....      EXPLCKRL       X'00' Used to release the
                                        exposure lock
     This flag is to keep the status information for this exposure.
0001    1 Bitstring    1 EXPSTATF       Exposure status flag
          00000000       EXPNOP         X'00' Indicates that neither a
                                        RSCH or a SSCH is required.
          00000001       EXPDQINP       X'01' Indicates a DEQUEUE in
                                        progress
          00000002       EXPRSCH        X'02' Indicates that a RSCH is
                                        required
          00000004       EXPSSCH        X'04' Indicates that a SSCH is
                                        required
0002    2 Bitstring    1 EXPTYPEF       Exposure type flag
          .... ..1.      EXPFBA         X'02' This is an FBA device
          .... ...1      EXPECKD        X'01' Indicates this is an ECKD
                                        paging device
0003    3 Bitstring    1 *              Reserved for future IBM use
     Maximum number of outstanding DASD I/O for multiple read or writes.
0004    4 Signed       2 EXPMAXMW       Maximum number of multiple writes
                                        that can be added into the
                                        channel program. This value is 4
                                        * number of records per track.
0006    6 Signed       2 EXPQCNEG       Number of times EXPCURQC went
                                        neg.
     The IORBK for this exposure
0008    8 Address      4 EXPFACPA       First Active Channel Program Addr
000C   12 Address      4 EXPSCCWP       Suspended CCW package. This is
                                        also the address of the last
                                        PIOBK in the current channel
                                        program.
     These are deferred saveareas when all CCW packages are used for this
     exposure. The saveareas are a single threaded list with the last
     pointer equal to zero.
0010   16 Address      4 EXPSFDSV       First deferred savearea for
                                        single reads and writes
0014   20 Address      4 EXPSCDSV       Current deferred savearea that
                                        will be dequeue for single reads
                                        and write
0018   24 Address      4 EXPMRDFQ       Queue anchor for deferred
                                        multiple read operations which
                                        are sorted in ascending order by
                                        cylinder number. The end of queue
                                        is zeroes
001C   28 Address      4 EXPMRCQ        Address of the current deferred
                                        read SAVBK which is the current
                                        active cylinder number.
0020   32 Address      4 EXPMWDFQ       Queue anchor for deferred
                                        multiple write operations which
                                        are sorted in ascending order by
                                        cylinder number. The end of queue
                                        is zeroes
0024   36 Address      4 EXPMWCQ        Address of the current deferred
                                        write SAVBK which is the current
                                        active cylinder number.
     Monitor counters.
0028   40 Signed       4 EXPCTPRD       Total count of page read
                                        operations for this device. Note
                                        that page read operations may be
                                        directed to devices without any
                                        cylinders specifically defined as
                                        type PAGE.
002C   44 Signed       4 EXPCTPWR       Total count of page write
                                        operations for this device. Note
                                        that page write operations may be
                                        directed to devices without any
                                        cylinders specifically defined as
                                        type PAGE.
0030   48 Signed       4 EXPCTSRD       Total count of spooling reads for
                                        this device.
0034   52 Signed       4 EXPCTSWR       Total count of spooling writes
                                        for this device.
0038   56 Signed       4 EXPCTACP       Total count of paging/spooling
                                        reads and writes added to an
                                        existing channel program without
                                        executing a SSCH or RSCH.
003C   60 Signed       4 EXPCURQC       Cardinal count of all outstanding
                                        paging/spooling reads/writes for
                                        this device.
0040   64 Signed       4 EXP2BQED       Count of slots that have been
                                        assigned on this CPVOL but have
                                        not yet been added to EXPCURQC
                                        (CPVOL because EXP2BQED is only
                                        valid in the first EXPBK for
                                        multi exposure devices). This
                                        count is updated using CS logic
0044   68 Address      4 EXPIORBK       IORBK for this exposure. The
                                        IORBK is always at the beginning
                                        of each PAGBK so this field
                                        doubles as the PAGBK address
          00000044       EXPPAGBK       EXPIORBK,4 PAGBK for this
                                        exposure
0048   72 Signed       4 EXPCTUSI       Total count of the number of
                                        times the channel program had to
                                        be terminated to allow user I/O.
                                        This is an indicator of
                                        interference between user and
                                        paging/spooling I/O.
004C   76 Signed       4 EXPDEVST       Exposure service time.
0050   80 Signed       4 EXPMLOAD       Exposure MLOAD.
0054   84 Signed       4 EXPTIMER       Exposure timestamp for SSCH/RSCH.
0058   88 Signed       4 EXPINTIM       Exposure timestamp at I/O
                                        interrupt time. ....
005C   92 Signed       4 EXPNMPIO       Number of active PIOBKS at I/O
                                        interrupt time used to calc
                                        service time.
0060   96 Address      4 EXPRDCBK       Address of the RDCBK.
0064  100 Signed       4 EXPCONT (20)   Count of 20 contiguous free
                                        spaces allocated from 1 to 20
                                        plus.
00B4  180 Signed       4 EXPBKEND (0)   End of EXPBK.
          000000B4       EXPBSIZE       *-EXPBK Size of this DSECT in
                                        Bytes
          00000017       EXPSIZE        (((*-EXPBK)+7)/8) Size in
                                        double-words
     The next three statements EXPQUENT, EXPQANCH, and EXPQCURR are used to
     map the multiple read and write queue fields EXPMRDFQ, EXPMRCQ and
     EXPMWDFQ, EXPMWCQ.

EXPQUENT DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      EXPQUENT       EXPOSURE BLOCK
0000    0 Address      4 EXPQANCH       Anchor for multiple defer queues.
0004    4 Address      4 EXPQCURR       Current pointer to CPEBK in
                                        queue.

 

EXPBK Storage Layout

          
*** EXPBK - EXPOSURE BLOCK
*
*     +------+------+------+------+-------------+-------------+
*   0 |:LCKFG|:STATF|:TYPEF|//////|  EXPMAXMW   |  EXPQCNEG   |
*     +------+------+------+------+-------------+-------------+
*   8 |         EXPFACPA          |         EXPSCCWP          |
*     +---------------------------+---------------------------+
*  10 |         EXPSFDSV          |         EXPSCDSV          |
*     +---------------------------+---------------------------+
*  18 |         EXPMRDFQ          |         EXPMRCQ           |
*     +---------------------------+---------------------------+
*  20 |         EXPMWDFQ          |         EXPMWCQ           |
*     +---------------------------+---------------------------+
*  28 |         EXPCTPRD          |         EXPCTPWR          |
*     +---------------------------+---------------------------+
*  30 |         EXPCTSRD          |         EXPCTSWR          |
*     +---------------------------+---------------------------+
*  38 |         EXPCTACP          |         EXPCURQC          |
*     +---------------------------+---------------------------+
*  40 |         EXP2BQED          |         EXPIORBK          |
*     +---------------------------+---------------------------+
*  48 |         EXPCTUSI          |         EXPDEVST          |
*     +---------------------------+---------------------------+
*  50 |         EXPMLOAD          |         EXPTIMER          |
*     +---------------------------+---------------------------+
*  58 |         EXPINTIM          |         EXPNMPIO          |
*     +---------------------------+---------------------------+
*  60 |         EXPRDCBK          |                           |
*     +---------------------------+                           |
*  68 |                                                       |
*     =                       EXPCONT                         =
*     |                           +---------------------------+
*     |                           |
*     +---------------------------+
*
*** EXPBK - EXPOSURE BLOCK
          
*** EXPQUENT - EXPOSURE BLOCK
*
*     +---------------------------+---------------------------+
*   0 |         EXPQANCH          |         EXPQCURR          |
*     +---------------------------+---------------------------+
*   8
*
*** EXPQUENT - EXPOSURE BLOCK

 

EXPBK Cross Reference

Symbol         Dspl Value
-------------- ---- -----
EXPBKEND       00B4
EXPBSIZE       00B4 000000B4
EXPCONT        0064
EXPCTACP       0038
EXPCTPRD       0028
EXPCTPWR       002C
EXPCTSRD       0030
EXPCTSWR       0034
EXPCTUSI       0048
EXPCURQC       003C
EXPDEVST       004C
EXPDQINP       0001 00000001
EXPECKD        0002 01
EXPFACPA       0008
EXPFBA         0002 02
EXPFLAGS       0000
EXPINTIM       0058
EXPIORBK       0044
EXPLCKFG       0000
EXPLCKRL       0000 00
EXPMAXMW       0004
EXPMLOAD       0050
EXPMRCQ        001C
EXPMRDFQ       0018
EXPMWCQ        0024
EXPMWDFQ       0020
EXPNMPIO       005C
EXPNOP         0001 00000000
EXPPAGBK       0044 00000044
EXPQANCH       0000
EXPQCNEG       0006
EXPQCURR       0004
EXPRDCBK       0060
EXPRSCH        0001 00000002
EXPSCCWP       000C
EXPSCDSV       0014
EXPSFDSV       0010
EXPSIZE        00B4 00000017
EXPSSCH        0001 00000004
EXPSTATF       0001
EXPTIMER       0054
EXPTYPEF       0002
EXP2BQED       0040

This information is based on z/VM V4R2.0. Last updated on 17 Oct 2001 at 15:50:01 EDT.
Copyright IBM Corporation, 1990, 2001