DXDA | Back to Index page

| Prolog Control Block Contents DXDA 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.

DXDA Prolog | Top of page

     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 HCPFMU/HCPFMP.
     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 HCPFMU/HCPFMP.
     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
     RELOCATION CONSIDERATIONS : None
     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 | Top of page

     DXDA DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      DXDA           Define Extent data area
    0000    0 Bitstring   32 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' DXDMWC Mask byte, bits 0
                                            and 1 ------- Codes for use with
                                            DXDMWC
              .... ....      DXDMWCH0       X'00' DXDMWCH0 Permit all write
                                            operations except write HA and
                                            Rec 0
              .1.. ....      DXDMWCIW       X'40' DXDMWCIW Inhibit all write
                                            operations
              1... ....      DXDMWCIF       X'80' DXDMWCIF Permit update
                                            write operations only
              11.. ....      DXDMWCPA       X'C0' DXDMWCPA 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' DXDAAM Attributes byte,
                                            bits 0 and 1 ------- Codes for
                                            use with DXDAAM
              11.. ....      DXDAAME        X'C0' DXDAAME 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' DXDRDF Regular data format
                                            mode
              .... 1...      DXDTSVAL       X'08' DXDTSVAL Time stamp valid
              .... .1..      DXDSTDR0       X'04' DXDSTDR0 Standard R0 Format
              .... ..1.      DXDEXPRM       X'02' DXDEXPRM Extended Parameter
                                            Bit
                 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
              00000010       DXDNXRCL       *-DXDAREA No XRC Support data
                                            length
                 Bytes 16 through 23 (time stamp)
    0010   16 Bitstring    8 DXDTSTAM       Time stamp
              00000018       DXDXRCL        *-DXDAREA XRC Support data length
                 Bytes 24 through 31
            CHECK TO SEE IF OTHER BITS SHOULD BE ADDED
    0018   24 Bitstring    1 DXDEPARM       Global attributes extended
              ..1. ....      DXDEB27        X'20' DXDEB27 Byte 27 has
                                            records/track
    0019   25 Bitstring    1 DXDPRIOR       Priority of IO
    001A   26 Bitstring    1 DXDXRC         XRC/CH extender
    001B   27 Bitstring    1 DXDRCDS        Byte 27 - records per track
    001C   28 Bitstring    4 DXDRSRVD       Reserved for hardware use
                 Length equates
              00000020       DXDBSIZE       *-DXDAREA Size of DXDA in bytes
              00000004       DXDSIZE        ((*-DXDAREA)+7)/8 Size of DXDA in
                                            DWs

DXDA Storage Layout | Top of page

    *** DXDA - Define Extent data area
    *
    *     +------+------+-------------+--------------------+------+
    *   0 |:MASK |:ATTR |  DXDBLKSZ   |////////////////////|:GLAE |
    *     +------+------+-------------+-------------+------+------+
    *   8 |  DXDBXCC    |  DXDBXHH    |  DXDEXCC    |  DXDEXHH    |
    *     +-------------+-------------+-------------+-------------+
    *  10 |                       DXDTSTAM                        |
    *     +------+------+------+------+---------------------------+
    *  18 |:EPARM|:PRIOR|DXDXRC|:RCDS |         DXDRSRVD          |
    *     +------+------+------+------+---------------------------+
    *  20
    *
    *** DXDA - Define Extent data area

DXDA Cross Reference | Top of page

    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       001C 00000020
    DXDBXADR       0008
    DXDBXCC        0008
    DXDBXHH        000A
    DXDCFW         0001 02
    DXDDFW         0001 01
    DXDEB27        0018 20
    DXDEPARM       0018
    DXDEXADR       000C
    DXDEXCC        000C
    DXDEXHH        000E
    DXDEXPRM       0007 02
    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
    DXDNXRCL       000E 00000010
    DXDPRIOR       0019
    DXDRCDS        001B
    DXDRDF         0007 40
    DXDRSRVD       001C
    DXDSIZE        001C 00000004
    DXDSTDR0       0007 04
    DXDTSTAM       0010
    DXDTSVAL       0007 08
    DXDXRC         001A
    DXDXRCL        0010 00000018
    DXDZEROS       0004

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:28:00 EDT.
Copyright IBM Corporation, 1990, 2020