DCHSECT Back to Index page
 
Prolog 
Control Block Contents 
   DCHSECT DSECT
Storage Layout 
Cross Reference (Contains links to field and bit definitions)
Programming Interface Information:
This information is NOT intended to be
used as Programming Interfaces of z/VM.


  DCHSECT Prolog Top of page
 
 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 Top of page
 

 DCHSECT DSECT Top of page
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 Top of page
 
 
*** 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 Top of page
 
 
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 6.4.0.
Last updated on 24 Aug 2016 at 09:21:01 EDT.
Copyright IBM Corporation, 1990, 2016