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