DVTRK

Prolog  

Control Block Contents  
   DVTRK DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  

DVTRK Prolog

 NAME       : HCPDVTRK
 DESCRIPTION: DASD Virtual TRacK list node
 DSECT      : DVTRK
 FUNCTION   : Contains information specific to DASD block
              I/O requests.  To be specific, this control
              block contains information regarding a
              particular track that was accessed (for write)
              during the process of one CMS block i/o
              request.  All tracks that were accessed
              for write have one of these control blocks
              created for them and these control blocks are
              linked together and anchored off of the DBCWK
              control block.
 LOCATED BY : DBCTFRST in the DBCWK control block.
              Also, any DVIENTRY that contains a block
              on the track represented by this DVTRK point
              to this control block.
 CREATED BY : HCPDPCUT macro in module HCPDBC
 DELETED BY : HCPDPSRP and/or HCPDPSCU (at cleanup time
              after an entire CMS block i/o request has
              completed).
 RELOCATION CONSIDERATIONS : None
 COMMENTS   : None

DVTRK Control Block Content

DVTRK DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      DVTRK          DASD Virtual TRacK list node
0000    0 Dbl-Word     8 * (0)          Better be double word aligned!
0000    0 Address      4 DVTFORW        Pointer to next DVTRK block
0004    4 Address      4 DVTTCHBK       TCHBK Address
0008    8 Signed       4 DVTCOUNT       Count of unscheduled i/os to
                                        track
000C   12 Signed       4 DVTTKDAT (0)   Track data, copied between here
                                        and HCPDBCWK, so it MUST match
000C   12 Signed       4 DVTCDATA       TCHBK Center data word contents
0010   16 Bitstring    1 DVTFILL        Filler, can't be used without
                                        changes to HCPDBC since data is
                                        copied directly
0011   17 Bitstring    3 DVTDPSTF (0)   DPSBK stuff about track
0011   17 Bitstring    1 DVTHIRN        Highest record num on track
0012   18 Signed       2 *              Reserved for IBM use
          00000002       DVTTKLEN       (*-DVTTKDAT+3)/4 Size of track
                                        data in words DVTRTRAK And
                                        DVTFTKEY must be grouped together
0014   20 Signed       4 DVTRTRAK       Relative track for this TCHBK
0018   24 Signed       4 DVTFTKEY       Key for this TCHBK DVTRTRAK And
                                        DVTFTKEY must be grouped together
001C   28 Bitstring    1 DVTFLAG        Processing bits
          1... ....      DVTDEL         X'80' DVTDEL Must delete this
                                        TCHBK on back end
          .1.. ....      DVTWFAIL       X'40' DVTWFAIL Write to cache not
                                        performed because track didn't
                                        exist
          ..1. ....      DVTRDF         X'20' DVTRDF Regular data format
001D   29 Bitstring    3 *              Reserved for IBM use
0020   32 Signed       4 *              Reserved for IBM use
0024   36 Signed       4 *              Reserved for IBM use
0028   40 Dbl-Word     8 * (0)          Must always be DWRD aligned
          00000028       DVTRKLEN       *-DVTRK Header size

DVTRK Storage Layout

          
*** DVTRK - DASD Virtual TRacK list node
*
*     +---------------------------+---------------------------+
*   0 |         DVTFORW           |         DVTTCHBK          |
*     +---------------------------+---------------------------+
*   8 |         DVTCOUNT          |         DVTCDATA          |
*     +------+------+-------------+---------------------------+
*  10 |:FILL |:HIRN |/////////////|         DVTRTRAK          |
*     +------+------+-------------+------+--------------------+
*  18 |         DVTFTKEY          |:FLAG |////////////////////|
*     +---------------------------+------+--------------------+
*  20 |///////////////////////////|///////////////////////////|
*     +---------------------------+---------------------------+
*  28
*
*** DVTRK - DASD Virtual TRacK list node

DVTRK Cross Reference

Symbol         Dspl Value
-------------- ---- -----
DVTCDATA       000C
DVTCOUNT       0008
DVTDEL         001C 80
DVTDPSTF       0011
DVTFILL        0010
DVTFLAG        001C
DVTFORW        0000
DVTFTKEY       0018
DVTHIRN        0011
DVTRDF         001C 20
DVTRKLEN       0028 00000028
DVTRTRAK       0014
DVTTCHBK       0004
DVTTKDAT       000C
DVTTKLEN       0012 00000002
DVTWFAIL       001C 40