Programming Interface Information: This information is NOT intended to be used as Programming Interfaces of z/VM.

#### DX2BK

Prolog

Control Block Contents
DX2BK DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### DX2BK Prolog

     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.
     COMMENTS   :

#### DX2BK Control Block Content

#### DX2BK DSECT

    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 EXPBK or MEXBK address, status
          field and the virtual device number.
    0C00 3072 Address      4 DX2EXPBK       Address of the EXPBK or MEXBK 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' Indicates this extent is
                                            invalid.
              .1.. ....      DX2READO       X'40' 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' 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

    *** 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

    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 V5R2.0. Last updated on 12 Apr 2006 at 16:52:35 EDT.
Copyright IBM Corporation, 1990, 2005