DX2BK Back to Index page
 
Prolog 
Control Block Contents 
   DX2BK 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.


  DX2BK Prolog Top of page
 
 NAME       : HCPDX2BK
 DESCRIPTION: Minidisk extent index level 2.
 DSECT      : DX2BK
 FUNCTION   : A DX2BK contains the minidisk extents for a
              minidisk-pool.
 LOCATED BY : HCPDX1BK  - DX1DX2Bk points to the DX2BK.
 CREATED BY : HCPAMD44  When a Diagnose 244 is issued by the user.
 DELETED BY : HCPAMD44  During an identify pool function the
              previous DX1BK will be deleted if any.
              HCPMSMDP  During storage reset operation.
 RELOCATION CONSIDERATIONS : None
 COMMENTS   :
 
 
  DX2BK Control Block Content Top of page
 

 DX2BK DSECT Top of page
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure DX2BK Minidisk extent index level 2. Each entry in this table represents one minidisk extent. This is the first part of an entry which is split into four parts. This part contains the pool-relative-block number start and end for the extent. 0000 0 Signed 4 DX2PRBNS Pool-Relative-block number (PRBN) start for this minidisk extent. 0004 4 Signed 4 DX2PRBNE PRBN end for this minidisk extent. 00000008 DX21ENT4 *-DX2PRBNS Used to get length of this entry. 0008 8 Dbl-Word 8 DX2PRBNX (127) Next entry in table This is the second part of an entry which is split into four parts. This part contains the device-relative-block number start and end for the extent. 0400 1024 Signed 4 DX2DRBNS Device-Relative-block number (DRBN) start for this minidisk extent. 0404 1028 Signed 4 DX2DRBNE DRBN end for this minidisk extent. 00000008 DX22ENT4 *-DX2DRBNS Used to get length of this entry. 0408 1032 Dbl-Word 8 DX2DRBNX (127) Next entry in table. This is the third part of an entry which is split into four parts. This part contains the minidisk's starting and ending cylinder or block numbers on the physical device. 0800 2048 Signed 4 DX2MEXT (0) Minidisk extent information 0800 2048 Signed 4 DX2MSEXT Minidisk starting cylinder (CKD/ ECKD) or 512-byte block (FBA) 0804 2052 Signed 4 DX2MEEXT Minidisk ending cylinder (CKD/ ECKD) or 512-byte block (FBA) 00000008 DX23ENT4 *-DX2MEXT Used to get length of this entry. 0808 2056 Dbl-Word 8 DX2MCYNX (127) Next entry in table. This is the fourth part of an entry which is split into four parts. This part contains the exposure block address, status field and the virtual device number. 0C00 3072 Address 4 DX2EXPBK Address of the EXPBK or HXPBK for these PRBN. 0C04 3076 Signed 2 DX2VDEVN Virtual device number for the minidisk. 0C06 3078 Bitstring 1 DX2STAT Status byte 1... .... DX2INVLD X'80' DX2INVLD Indicates this extent is invalid. .1.. .... DX2READO X'40' DX2READO Indicates that this extent is on a read only DASD. If this extent is mapped the PTE should have the page protect bit set on. ..1. .... DX2FBA X'20' DX2FBA Indicates that this minidisk extent resides on an FBA device 0C07 3079 Bitstring 1 * Reserved for IBM use. 00000008 DX24ENT4 *-DX2EXPBK Used to get length of this entry. 0C08 3080 Dbl-Word 8 DX2EXPNX (127) Next entry in table. The following equates are used to get the number of entries that will fit in a page. DX2ETBSZ is the total size in bytes of all the parts of an entry. DX2NMENT is the total number of entries that will fit in a page. 00000020 DX2ETBSZ (DX21ENT4+DX22ENT4+DX23ENT4+DX24E NT4) 00000080 DX2NMENT 4096/DX2ETBSZ If the number of entries that can be contained in this control block decreases to 127 or lower then HCPDX1BK will have to increase to two or more contiguous pages. Therefore the following statement will fail when the number of entries decreases to 127 or lower.
 
 
  DX2BK Storage Layout Top of page
 
          
*** DX2BK - Minidisk extent index level 2.
*
*     +---------------------------+---------------------------+
*   0 |         DX2PRBNS          |         DX2PRBNE          |
*     +---------------------------+---------------------------+
*   8 |                                                       |
*     =                       DX2PRBNX                        =
*     |                                                       |
*     +---------------------------+---------------------------+
* 400 |         DX2DRBNS          |         DX2DRBNE          |
*     +---------------------------+---------------------------+
* 408 |                                                       |
*     =                       DX2DRBNX                        =
*     |                                                       |
*     +---------------------------+---------------------------+
* 800 |         DX2MSEXT          |         DX2MEEXT          |
*     +---------------------------+---------------------------+
* 808 |                                                       |
*     =                       DX2MCYNX                        =
*     |                                                       |
*     +---------------------------+-------------+------+------+
* C00 |         DX2EXPBK          |  DX2VDEVN   |:STAT |//////|
*     +---------------------------+-------------+------+------+
* C08 |                                                       |
*     =                       DX2EXPNX                        =
*     |                                                       |
*     +-------------------------------------------------------+
*1000
*
*** DX2BK - Minidisk extent index level 2.
 
 
  DX2BK Cross Reference Top of page
 
 
Symbol         Dspl Value
-------------- ---- -----
DX2DRBNE       0404
DX2DRBNS       0400
DX2DRBNX       0408
DX2ETBSZ       0C08 00000020
DX2EXPBK       0C00
DX2EXPNX       0C08
DX2FBA         0C06 20
DX2INVLD       0C06 80
DX2MCYNX       0808
DX2MEEXT       0804
DX2MEXT        0800
DX2MSEXT       0800
DX2NMENT       0C08 00000080
DX2PRBNE       0004
DX2PRBNS       0000
DX2PRBNX       0008
DX2READO       0C06 40
DX2STAT        0C06
DX2VDEVN       0C04
DX21ENT4       0004 00000008
DX22ENT4       0404 00000008
DX23ENT4       0804 00000008
DX24ENT4       0C07 00000008
 
This information is based on z/VM 7.3.0 Last updated on 22 Jun 2022 at 15:50:06 EDT.
Copyright IBM Corporation, 1990, 2022