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 DSECT
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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 - 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.

 
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