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

DXDA

Prolog  

Control Block Contents  
   DXDA DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  


DXDA Prolog

 Name       : HCPDXDA
 Description: Define Extent data area
 DSECT      : DXDA
 Function   : Maps the contents of the Define Extent data
              area.
 Located by : HCCWADDR - The Define Extent CCW data address field
              contains the address of the define
              extent data area.
 Created by :
              Storage for this control block cannot be
              specifically allocated/deallocated using
              HCPGETST/HCPRELST.
              Paging I/O manager -
              Data area resides in the HCPPAGBK which
              is allocated by HCPRDA.
              Track cache manager -
              Data area is part of a larger free storage
              area used to build ECKD channel programs
              which is allocated in modules HCPFTU/HCPFTP.
 Deleted by :
              Storage for this control block cannot be
              specifically allocated/deallocated using
              HCPGETST/HCPRELST.
              Paging I/O manager -
              Data area resides in the HCPPAGBK which
              is deallocated by HCPRDD.
              Track cache manager -
              Data area is part of a larger free storage
              area used to build ECKD channel programs
              which is deallocated in modules HCPFTU/HCPFTP.
 Serialized :
              Paging I/O manager -
              EXPLCKFG - The paging I/O manager uses the exposure
              block lock to serialize this data area.
              Track cache manager -
              TCMTSLK  - Track cache lock
 Comments   :
              Paging I/O manager -
              There is one define extent data area for each
              ECKD paging exposure. The data area resides
              in the HCPPAGBK (where the set paging parameter
              CCW would exist (but doesn't for ECKD devices)).
              ALL the Define Extent CCWs in the volume's PIOBKs
              contain the address of this one data area.
              Track cache manager -
              None

 

DXDA Control Block Content


DXDA DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      DXDA           Define Extent data area
0000    0 Bitstring   16 DXDAREA (0)    Define extent data area
     Byte 0 (Mask byte)
     Although defined as BITs, the contents of the mask byte are,
     architecturally, multiple codes.
0000    0 Bitstring    1 DXDMASK        Mask
          11.. ....      DXDMWC         X'C0' Mask byte, bits 0 and 1
                                        ------- Codes for use with DXDMWC
          .... ....      DXDMWCH0       X'00' Permit all write operations
                                        except write HA and Rec 0
          .1.. ....      DXDMWCIW       X'40' Inhibit all write
                                        operations
          1... ....      DXDMWCIF       X'80' Permit update write
                                        operations only
          11.. ....      DXDMWCPA       X'C0' Permit all write commands
                                        -------
          ..1. ....      DXDMNU         X'20' Mask byte, bit 2 (not used)
          ...1 1...      DXDMSC         X'18' Mask byte, bits 3 and 4
                                        ------- Codes for use with DXDMSC
          .... ....      DXDMSCPA       X'00' Permit all seek commands
          .... 1...      DXDMSCCH       X'08' Permit seek cyl/head
                                        commands
          ...1 ....      DXDMSCH        X'10' Permit seek head commands
          ...1 1...      DXDMSCIS       X'18' Inhibit all seek commands
                                        -------
          .... .11.      DXDMAA         X'06' Mask byte, bits 5 and 6
                                        ------- Codes for use with DXDMAA
          .... ....      DXDMAAN        X'00' Normal authorization
          .... ..1.      DXDMAADE       X'02' Device support
                                        authorization
          .... .1..      DXDMAADI       X'04' Diagnostic authorization
          .... .11.      DXDMAADR       X'06' Device support
                                        authorization with inhibit data
                                        check correction and retry
                                        -------
          .... ...1      DXDMPCI        X'01' Mask byte, bit 7
     Byte 1 (Attribute byte)
     This byte, like the mask byte, contains multiple codes. See the
     explaination of the mask byte for possible ways to manipulate the
     codes.
0001    1 Bitstring    1 DXDATTR        Global Attributes
          11.. ....      DXDAAM         X'C0' Attributes byte, bits 0 and
                                        1 ------- Codes for use with
                                        DXDAAM
          11.. ....      DXDAAME        X'C0' ECKD mode --------
          ..1. ....      DXDACMON       X'20' CKD conversion mode on
          ...1 11..      DXDASO         X'1C' Attributes byte, bits 3, 4,
                                        and 5 ------- Codes for use with
                                        DXDASO
          .... ....      DXDASONR       X'00' Normal cache replacement
          .... .1..      DXDASOBC       X'04' Bypass cache
          .... 1...      DXDASOIL       X'08' Inhibit cache loading
          .... 11..      DXDASOSA       X'0C' Sequential access
          ...1 .1..      DXDARECA       X'14' Record access
          .... 1...      DXDARECN       X'08' Inverse of record access
                                        -------
          .... ..1.      DXDCFW         X'02' Cache fast write
          .... ...1      DXDDFW         X'01' DASD fast write
     Bytes 2 and 3 (block size)
0002    2 Bitstring    2 DXDBLKSZ       Block size
     Bytes 4 through 7 (global attributes extended and reserved)
0004    4 Bitstring    4 DXDZEROS (0)   Reserved on some devices
0004    4 Bitstring    3 *
0007    7 Bitstring    1 DXDGLAE        Global attributes extended
          .1.. ....      DXDRDF         X'40' Regular data format mode
          .... .1..      DXDSTDR0       X'04' Standard R0 Format
     Bytes 8 through 11 (beginning extent address)
0008    8 Bitstring    4 DXDBXADR (0)   Beg extent address, CCHH
0008    8 Bitstring    2 DXDBXCC        CC of beginning CCHH
000A   10 Bitstring    2 DXDBXHH        HH of beginning CCHH
     Bytes 12 through 15 (ending extent address)
000C   12 Bitstring    4 DXDEXADR (0)   Ending extent address, CCHH
000C   12 Bitstring    2 DXDEXCC        CC of ending CCHH
000E   14 Bitstring    2 DXDEXHH        HH of ending CCHH
     Length equates
          00000010       DXDBSIZE       *-DXDAREA Size of DXDA in bytes
          00000002       DXDSIZE        ((*-DXDAREA)+7)/8 Size of DXDA in
                                        DWs

 

DXDA Storage Layout

          
*** DXDA - Define Extent data area
*
*     +------+------+-------------+--------------------+------+
*   0 |:MASK |:ATTR |  DXDBLKSZ   |////////////////////|:GLAE |
*     +------+------+-------------+-------------+------+------+
*   8 |  DXDBXCC    |  DXDBXHH    |  DXDEXCC    |  DXDEXHH    |
*     +-------------+-------------+-------------+-------------+
*  10
*
*** DXDA - Define Extent data area

 

DXDA Cross Reference

Symbol         Dspl Value
-------------- ---- -----
DXDAAM         0001 C0
DXDAAME        0001 C0
DXDACMON       0001 20
DXDAREA        0000
DXDARECA       0001 14
DXDARECN       0001 08
DXDASO         0001 1C
DXDASOBC       0001 04
DXDASOIL       0001 08
DXDASONR       0001 00
DXDASOSA       0001 0C
DXDATTR        0001
DXDBLKSZ       0002
DXDBSIZE       000E 00000010
DXDBXADR       0008
DXDBXCC        0008
DXDBXHH        000A
DXDCFW         0001 02
DXDDFW         0001 01
DXDEXADR       000C
DXDEXCC        000C
DXDEXHH        000E
DXDGLAE        0007
DXDMAA         0000 06
DXDMAADE       0000 02
DXDMAADI       0000 04
DXDMAADR       0000 06
DXDMAAN        0000 00
DXDMASK        0000
DXDMNU         0000 20
DXDMPCI        0000 01
DXDMSC         0000 18
DXDMSCCH       0000 08
DXDMSCH        0000 10
DXDMSCIS       0000 18
DXDMSCPA       0000 00
DXDMWC         0000 C0
DXDMWCH0       0000 00
DXDMWCIF       0000 80
DXDMWCIW       0000 40
DXDMWCPA       0000 C0
DXDRDF         0007 40
DXDSIZE        000E 00000002
DXDSTDR0       0007 04
DXDZEROS       0004

This information is based on z/VM V4R1.0.
Last updated on 5 Jun 2001 at 13:30:26 EDT.
Copyright IBM Corporation, 1990, 2001