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

#### DCHSECT

Prolog

Control Block Contents
DCHSECT DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### DCHSECT Prolog

     Name       : DCH
     Description: Data Control Hyperblock
     DSECT      : DCHSECT
     Notes      : MODULE TYPE - Macro
     Function   : This is the bilingual macro
                  containing the mapping of the data control
                  hyperblock, used to contain cached or accessed
                  FSTs for both SFS directories and CMS formatted
                  minidisks.

#### DCHSECT Control Block Content

#### DCHSECT DSECT

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      DCHSECT        Data Control Hyperblock
    0000    0 Address      4 DCHFWPTR       FORWARD POINTER
    0004    4 Address      4 DCHBWPTR       BACKWARD POINTER
    0008    8 Signed       4 DCHDWSIZ       FULL HYPERBLK STOR SIZE IN DWORDS
    000C   12 Address      4 DCHTRUNK       ADDR OF NEXT BLK UP IN STRUCTURE
    000C   12 Signed       4 DCHFSTIU       Count of used FSTs in Caching HB
    0010   16 Signed       4 DCHTDISP       DISP TO DISK ADR IN TRUNK PTR BLK
    0010   16 Address      4 DCHDSPTR       Address of data space hyperblock
    0014   20 Signed       4 DCHDTSIZ       DATA PORTION SIZE IN BYTES
    0018   24 Signed       4 DCHSEQBD       SEQUENTIAL DATA BLK DISPLACEMENT
    001C   28 Bitstring    1 DCHFLG1        DCH FLAG 1
         **      EQUATES FOR DCHFLG1
              1... ....      DCHCHOP        X'80' DEALLOC THIS DIR. BLK.
                                            DURING DIRECTORY UPDATE
              .1.. ....      DCHNEW         X'40' DO NOT REALLOC THIS DIR.
                                            BLK. DURING DIRECTORY UPDATE
              ..1. ....      DCHDALLO       X'20' DISK ADDRESS OF BLOCK IS IN
                                            DE-ALLOCATION LIST
              ...1 ....      DCHCHGD        X'10' BLOCK HAS BEEN ALTERED
              .... 1...      DCHRALLO       X'08' DISK ADDRESS OF BLOCK IS IN
                                            RE-ALLOCATION LIST
              .... .1..      DCHAUX         X'04' AUX DIR HAS BEEN CREATED
    001D   29 Bitstring    1 DCHFLG2        DCH FLAG 2 ** EQUATES FOR DCHFLG2
              1... ....      DCHFULL        X'80' ALL DSK BLKS ALLOC'D IN
                                            THIS HBLK
              .1.. ....      DCHDA          X'40' ALL DSK BLKS DEALLOCATED BY
                                            ERS
              ..1. ....      DCHLHBLK       X'20' LAST HBLK IN BUFFER CH FOR
                                            ERS
              ...1 ....      DCHDUM         X'10' DUMMY HBLK FOR CHAINING AUX
                                            DIR
              .... 1...      DCHSHR         X'08' BLK IS IN SHARED STORAGE
    001E   30 Bitstring    1 DCHFLG3        DCH FLAG 3 - RESERVED -
    001F   31 Bitstring    1 DCHFLG4        DCH FLAG 4 - RESERVED - 2 Fields
                                            used only for alloc map
    0020   32 Signed       4 DCHDAMAP       DEALLOCATION MAP ADDRESS
    0024   36 Signed       4 DCHCHMAP       CHANGE MAP ADDRESS
    0020   32 Signed       4 DCHYDISP       Pointer block displacement used
                                            by DMSERC for file truncation.
    0024   36 Signed       4 DCHCOUNT       Data block count used (lvl 1
                                            only) by DMSERC for file
                                            truncation.
    0020   32 Signed       4 DCHOFFST       Offset into data block by DMSERC
                                            for file truncation.
    0024   36 Signed       4 DCHLSTRC       Last record in V-file used by
                                            DMSERC for file truncation.
    0028   40 Signed       4 DCHBUFAD       Hyperblock buffer address for
                                            read/only Stat minidisks.
    002C   44 Signed       4 *              reserved
    0030   48 Dbl-Word     8 * (0)
              00000030       DCHPFIXL       *-DCHSECT LENGTH OF PREFIX
                                            PORTION OF HBLK
    0030   48 Dbl-Word     8 DCHDATA (0)

#### DCHSECT Storage Layout

    *** DCHSECT - Data Control Hyperblock
    *
    *     +---------------------------+---------------------------+
    *   0 |         DCHFWPTR          |         DCHBWPTR          |
    *     +---------------------------+---------------------------+
    *   8 |         DCHDWSIZ          |         DCHTRUNK          |
    *     +---------------------------+---------------------------+
    *  10 |         DCHTDISP          |         DCHDTSIZ          |
    *     +---------------------------+------+------+------+------+
    *  18 |         DCHSEQBD          |:FLG1 |:FLG2 |:FLG3 |:FLG4 |
    *     +---------------------------+------+------+------+------+
    *  20 |         DCHDAMAP          |         DCHCHMAP          |
    *     +---------------------------+---------------------------+
    *  28 |         DCHBUFAD          |///////////////////////////|
    *     +---------------------------+---------------------------+
    *
    *** DCHSECT - Data Control Hyperblock

    *** Overlay for DCHTRUNK in DCHSECT
    *
    *                                 +---------------------------+
    *   8 ...                       C |         DCHFSTIU          |
    *                                 +---------------------------+
    *  10
    *
    *** Overlay for DCHTRUNK in DCHSECT

    *** Overlay for DCHTDISP in DCHSECT
    *
    *     +---------------------------+
    *  10 |         DCHDSPTR          | 14
    *     +---------------------------+
    *
    *** Overlay for DCHTDISP in DCHSECT

    *** Overlay for DCHDAMAP in DCHSECT
    *
    *     +---------------------------+---------------------------+
    *  20 |         DCHYDISP          |         DCHCOUNT          |
    *     +---------------------------+---------------------------+
    *  28
    *
    *** Overlay for DCHDAMAP in DCHSECT

    *** Overlay for DCHDAMAP in DCHSECT
    *
    *     +---------------------------+---------------------------+
    *  20 |         DCHOFFST          |         DCHLSTRC          |
    *     +---------------------------+---------------------------+
    *  28
    *
    *** Overlay for DCHDAMAP in DCHSECT

#### DCHSECT Cross Reference

    Symbol         Dspl Value
    -------------- ---- -----
    DCHAUX         001C 04
    DCHBUFAD       0028
    DCHBWPTR       0004
    DCHCHGD        001C 10
    DCHCHMAP       0024
    DCHCHOP        001C 80
    DCHCOUNT       0024
    DCHDA          001D 40
    DCHDALLO       001C 20
    DCHDAMAP       0020
    DCHDATA        0030
    DCHDSPTR       0010
    DCHDTSIZ       0014
    DCHDUM         001D 10
    DCHDWSIZ       0008
    DCHFLG1        001C
    DCHFLG2        001D
    DCHFLG3        001E
    DCHFLG4        001F
    DCHFSTIU       000C
    DCHFULL        001D 80
    DCHFWPTR       0000
    DCHLHBLK       001D 20
    DCHLSTRC       0024
    DCHNEW         001C 40
    DCHOFFST       0020
    DCHPFIXL       0030 00000030
    DCHRALLO       001C 08
    DCHSEQBD       0018
    DCHSHR         001D 08
    DCHTDISP       0010
    DCHTRUNK       000C
    DCHYDISP       0020

This information is based on z/VM V6R1.0.
Last updated on 23 Oct 2009 at 11:00:28 EDT.
Copyright IBM Corporation, 1990, 2008