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

MEXBK

Prolog  

Control Block Contents  
   MEXBK DSECT
   MEXENTRY DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  


MEXBK Prolog

 NAME       : HCPMEXBK
 DESCRIPTION: MULTIPLE EXPOSURE BLOCK
 DSECT      : MEXBK
 FUNCTION   : CONTAINS THE NECESSARY INFORMATION TO FIND EACH EXPOSURE
              FOR MULTIPLE EXPOSURE DEVICES.
 LOCATED BY : RDEVEXPB FIELD OF RDEV  - POINTER TO MEXBK
 CREATED BY : HCPRDAAT - DURING ATTACH OF A MULTIPLE EXPOSURE DASD DEVICE
 DELETED BY : HCPRDADT - DURING DETACH OF A MULTIPLE EXPOSURE DASD DEVICE

 

MEXBK Control Block Content


MEXBK DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      MEXBK          MULTIPLE EXPOSURE BLOCK
0000    0 Bitstring    1 MEXCTEXP       Count of exposure blocks.
0001    1 Bitstring    1 *              Reserved for IBM use.
     This is information for multiple exposure blocks. This information
     indicates what exposure to use next for the reads or writes.
0002    2 Bitstring    6 MEXRDWRI (0)
0002    2 Bitstring    1 MEXFRDEX       First read exposure
0003    3 Bitstring    1 MEXLRDEX       Last read exposure
0004    4 Bitstring    1 MEXCREAD       Current available read exposure
     These are the write exposures.
0005    5 Bitstring    1 MEXFWREX       First available write exposures
0006    6 Bitstring    1 MEXLWREX       Last write exposure
0007    7 Bitstring    1 MEXCWRIT       Current available write exposure
0008    8 Address      4 MEX1STEX       Address of location of the first
                                        exposure block.
000C   12 Signed       4 *              Reserved for IBM use.
0010   16 Bitstring   16 MEXEXPBK (0)   Address of the first exposure
                                        block.
0010   16 Address      4 *              Place for exposure block address.
          00000004       MEXENTLN       *-MEXEXPBK Length of an entry.
0014   20 Address      4 MEXNXTEX (3)   Place for three exposure block
                                        addresses.
          00000004       MEXEXPEC       L'MEXEXPBK/MEXENTLN Count of
                                        entries in the exposure block
                                        field MEXEXPBK.
          00000020       MEXLEN         *-MEXBK
          00000004       MEXSIZE        (MEXLEN+7)/8 Number of
                                        doublewords.
     Use this to DSECT the read and write areas MEXFRDEX, MEXLRDEX, MEXCRDIT
     and MEXFWREX, MEXLWREX, MEXCWRIT.

MEXENTRY DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      MEXENTRY       MULTIPLE EXPOSURE BLOCK
0000    0 Bitstring    1 MEXFIRST       First available write exposures
0001    1 Bitstring    1 MEXLAST        Last write exposure
0002    2 Bitstring    1 MEXCURR        Current available write exposure

 

MEXBK Storage Layout

          
*** MEXBK - MULTIPLE EXPOSURE BLOCK
*
*     +------+------+------+------+------+------+------+------+
*   0 |:CTEXP|//////|:FRDEX|:LRDEX|:CREAD|:FWREX|:LWREX|:CWRIT|
*     +------+------+------+------+------+------+------+------+
*   8 |         MEX1STEX          |///////////////////////////|
*     +---------------------------+---------------------------+
*  10 |///////////////////////////|         MEXNXTEX          |
*     +---------------------------+                           |
*     |                                                       |
*     +-------------------------------------------------------+
*  20
*
*** MEXBK - MULTIPLE EXPOSURE BLOCK
          
*** MEXENTRY - MULTIPLE EXPOSURE BLOCK
*
*     +------+------+------+
*   0 |:FIRST|:LAST |:CURR | 3
*     +------+------+------+
*
*** MEXENTRY - MULTIPLE EXPOSURE BLOCK

 

MEXBK Cross Reference

Symbol         Dspl Value
-------------- ---- -----
MEXCREAD       0004
MEXCTEXP       0000
MEXCURR        0002
MEXCWRIT       0007
MEXENTLN       0010 00000004
MEXEXPBK       0010
MEXEXPEC       0014 00000004
MEXFIRST       0000
MEXFRDEX       0002
MEXFWREX       0005
MEXLAST        0001
MEXLEN         0014 00000020
MEXLRDEX       0003
MEXLWREX       0006
MEXNXTEX       0014
MEXRDWRI       0002
MEXSIZE        0014 00000004
MEX1STEX       0008

This information is based on z/VM V4R1.0.
Last updated on 5 Jun 2001 at 14:23:01 EDT.
Copyright IBM Corporation, 1990, 2001