IBM: DFDA

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.

DFDA

Prolog

Control Block Contents

DFDA DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

DFDA Prolog

 Name       : HCPDFDA
 DESCRIPTION: FBA Define Extent data area
 STATUS     : VM/ESA Version 2, Release 3.0
 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 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 FBA 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
              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


DFDA DSECT
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' Mask byte, bits 0 and 1
                                        ------- Codes for use with DFDMWC
          .... ....      DFDMWCNF       X'00' Non-formatting write
                                        permitted, formatting wirte
                                        inhibited
          .1.. ....      DFDMWCIW       X'40' Inhibit all write
                                        operations
          1... ....      DFDMWCRS       X'80' Reserved
          11.. ....      DFDMWCPA       X'C0' 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

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