DFDA | Back to Index page

| Prolog Control Block Contents DFDA 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.

DFDA Prolog | Top of page

     NAME       : HCPDFDA
     DESCRIPTION: FBA Define Extent data area
     DSECT      : DFDA
     FUNCTION   : Maps the contents of the Define Extent data
                  area for FBA devices.
     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 FBA 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 FBA 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
                  FBA paging exposure. The data area resides
                  in the HCPPAGBK (where the set paging parameter
                  CCW would exist (but doesn't for FBA  devices)).
                  ALL the Define Extent CCWs in the volume's PIOBKs
                  contain the address of this one data area.
                  Track cache manager -
                  None

DFDA Control Block Content | Top of page

     DFDA DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      DFDA           FBA Define Extent data area
    0000    0 Bitstring   16 DFDAREA (0)    FBA 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 DFDMASK        Mask
              11.. ....      DFDMWC         X'C0' DFDMWC Mask byte, bits 0
                                            and 1 ------- Codes for use with
                                            DFDMWC
              .... ....      DFDMWCNF       X'00' DFDMWCNF Non-formatting
                                            write permitted, formatting wirte
                                            inhibited
              .1.. ....      DFDMWCIW       X'40' DFDMWCIW Inhibit all write
                                            operations
              1... ....      DFDMWCRS       X'80' DFDMWCRS Reserved
              11.. ....      DFDMWCPA       X'C0' DFDMWCPA Permit all write
                                            commands
              ..1. ....      DFDMB2         X'20' Mask, bit 2 (not used)
                                            zeroes
              ...1 ....      DFDMB3         X'10' Mask, bit 3 (not used)
                                            zeroes
              .... 1...      DFDMB4         X'08' Mask, bit 4 ------- Codes
                                            for use with DFDMB4
              .... ....      DFDMB4DA       X'00' Data area
              .... 1...      DFDMB4ND       X'08' Non-data area
              .... .11.      DFDMB5         X'06' Mask byte, bit 5 -------
                                            Codes for use with DFDMB5
              .... ....      DFDMB5ID       X'00' Inhibit diagnostic commands
              .... .11.      DFDMB5PD       X'06' Permit diagnostic commands
              .... ..11      DFDMB6         X'03' Mask byte, bits 6 and 7
                                            ------- Codes for use with DFDMB6
              .... ....      DFDMB6CE       X'00' CE area
              .... ...1      DFDMB6S1       X'01' Subsystem 1 area
              .... ..1.      DFDMB6S2       X'02' Subsystem 2 area
              .... ..11      DFDMB6RS       X'03' Reserved
                 Byte 1 (must be zero)
    0001    1 Bitstring    1 DFDZERO        Reserved, must be zero
                 Bytes 2 and 3 (block size)
    0002    2 Bitstring    2 DFDBLKSZ       Block size in bytes
                 Bytes 4 through 7 (Extent Locator)
    0004    4 Bitstring    4 DFDEXTLC       Extent Locator for this extent
                 Bytes 8 through 11 (beginning extent address)
    0008    8 Bitstring    4 DFDBXBEG       Beg extent address in block
                                            number
                 Bytes 12 through 15 (ending extent address)
    000C   12 Bitstring    4 DFDEXEND       Ending extent block number
                 Length equates
              00000010       DFDBSIZE       *-DFDAREA Size of DFDA in bytes
              00000002       DFDSIZE        ((*-DFDAREA)+7)/8 Size of DFDA in
                                            DWs

DFDA Storage Layout | Top of page

    *** DFDA - FBA Define Extent data area
    *
    *     +------+------+-------------+---------------------------+
    *   0 |:MASK |:ZERO |  DFDBLKSZ   |         DFDEXTLC          |
    *     +------+------+-------------+---------------------------+
    *   8 |         DFDBXBEG          |         DFDEXEND          |
    *     +---------------------------+---------------------------+
    *  10
    *
    *** DFDA - FBA Define Extent data area

DFDA Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    DFDAREA        0000
    DFDBLKSZ       0002
    DFDBSIZE       000C 00000010
    DFDBXBEG       0008
    DFDEXEND       000C
    DFDEXTLC       0004
    DFDMASK        0000
    DFDMB2         0000 20
    DFDMB3         0000 10
    DFDMB4         0000 08
    DFDMB4DA       0000 00
    DFDMB4ND       0000 08
    DFDMB5         0000 06
    DFDMB5ID       0000 00
    DFDMB5PD       0000 06
    DFDMB6         0000 03
    DFDMB6CE       0000 00
    DFDMB6RS       0000 03
    DFDMB6S1       0000 01
    DFDMB6S2       0000 02
    DFDMWC         0000 C0
    DFDMWCIW       0000 40
    DFDMWCNF       0000 00
    DFDMWCPA       0000 C0
    DFDMWCRS       0000 80
    DFDSIZE        000C 00000002
    DFDZERO        0001

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:27:43 EDT.
Copyright IBM Corporation, 1990, 2020