Programming Interface Information:
This information is NOT
intended to be
used as Programming Interfaces of VM/ESA. It is to be
used for diagnosis only.
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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 |///////////////////////////|
* +---------------------------+---------------------------+
* 30 | |
* = DCHDATA =
* | |
* +-------------------------------------------------------+
*
*** 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 (contains links to field and bit definitions)
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 VM/ESA 2.4.0.
Last updated on 12 Aug 1999 at 11:18:47 EDT.
Copyright IBM Corporation, 1990, 1999
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