EXTBK

Prolog  

Control Block Contents  
   EXTBK DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  

EXTBK Prolog

 NAME       : HCPEXTBK
 DESCRIPTION: Extent Block
 DSECT      : EXTBK
 FUNCTION   : Describes a group of contiguous cylinders or slots
              on a CP-owned DASD containing the same allocation type.
 LOCATED BY : VEXPGEXT
              VEXSPEXT
              VEXTDEXT
              VEXDREXT
              VEXPEEXT
              VEX1SEXT
              EXTMYEXT
              EXTANYEX
 CREATED BY : HCPRDX when a CP-owned device is attached
              to the system
 DELETED BY : HCPRDD when a CP-owned device is detached
              from the system
 REFERENCES : HCPMSABK  - Map for Slot Allocation
              HCPMDISK  - Minidisk block
 SERIALIZED : Allocation locks
 NOTES      : EXTBKs of type PERM use only the following fields:
              EXTVEXBK, EXTSTART, EXTEND, EXTANYEX, and EXTMYEXT.
              EXTBKs are not created for type PARM or UNDF, as
              they are not needed in the internal representation
              of the allocation map.

EXTBK Control Block Content

EXTBK DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      EXTBK          Extent Block
0000    0 Signed       4 EXTVEXBK       Pointer back to VEXBK
     The following 2 fields vary in units depending on the type of device.
0004    4 Signed       4 EXTSTART       Starting cylinder (CKD/ECKD) or
                                        slot (FBA) for this extent
0008    8 Signed       4 EXTEND         Ending cylinder (CKD/ECKD) or
                                        slot (FBA) for this extent
000C   12 Signed       4 EXTINUSE       Number in use in this EXTBK. In
                                        cylinders for E/CKD TDSK and DRCT
                                        extents. In slots for E/CKD PAGE
                                        and SPOL extents and for all FBA
                                        extents. Not used for PERM.
0010   16 Signed       4 EXTHIGH        Highest slot or cylinder in use
                                        in this extent. Used only by TDSK
                                        and DRCT extents. This number is
                                        relative to the start of the
                                        volume. Query Alloc will actually
                                        report this number relative to
                                        the start of the extent.
0014   20 Signed       4 EXTSTRCT       Pointer to a structure which
                                        further describes what parts of
                                        the extent are in use. For PAGE
                                        and SPOL this points to a MSABK.
                                        For TDSK, this points to an MDISK
                                        block. Equals 0 for DRCT and PERM
                                        extents.
0018   24 Signed       4 EXTANYEX       Pointer to next extent on volume
                                        of any type. (for Q ALLOC MAP)
001C   28 Signed       4 EXTMYEXT       Pointer to next extent on volume
                                        of this type
0020   32 Signed       4 EXTSTSLT       Slot number of first slot in
                                        EXTBK. Same as EXTSTART for FBA
                                        devices.
0024   36 Signed       4 EXTENSLT       Slot number of last slot in
                                        EXTBK. Same as EXTEND for FBA
                                        devices.
0028   40 Signed       4 EXTFREE        Number of free slots in this
                                        extent when stopped allocating
                                        from this extent. Used to
                                        determine if need to get new
                                        CASBKs.
002C   44 Signed       4 EXTSLOTS       Number of slots in this extent
0030   48 Bitstring    1 EXTTYPE        Allocation type for this extent
0031   49 Bitstring    1 EXTFLAG        Flag byte
          1... ....      EXTFULL        X'80' Indicates entire extent is
                                        in use
          .1.. ....      EXTLOG1        X'40' This EXTBK is the first in
                                        a series of EXTBKs associated
                                        with 1 physical extent on the
                                        DASD
          ..1. ....      EXTLOGEX       X'20' This EXTBK belongs to a
                                        series of EXTBKs associated with
                                        1 physical extent on the DASD.
                                        This EXTBK is not the first EXTBK
                                        in the series.
0032   50 Signed       2 *              Reserved for IBM use
          00000007       EXTSIZE        (*-EXTBK+7)/8 Size, in
                                        doublewords, of EXTBK
          00000034       EXTSIZEB       *-EXTBK Size of EXTBK in bytes
          0000004E       EXTPRPG        (4096-24)/EXTSIZEB Maximum number
                                        of EXTBKs per page

EXTBK Storage Layout

          
*** EXTBK - Extent Block
*
*     +---------------------------+---------------------------+
*   0 |         EXTVEXBK          |         EXTSTART          |
*     +---------------------------+---------------------------+
*   8 |          EXTEND           |         EXTINUSE          |
*     +---------------------------+---------------------------+
*  10 |         EXTHIGH           |         EXTSTRCT          |
*     +---------------------------+---------------------------+
*  18 |         EXTANYEX          |         EXTMYEXT          |
*     +---------------------------+---------------------------+
*  20 |         EXTSTSLT          |         EXTENSLT          |
*     +---------------------------+---------------------------+
*  28 |         EXTFREE           |         EXTSLOTS          |
*     +------+------+-------------+---------------------------+
*  30 |:TYPE |:FLAG |/////////////| 34
*     +------+------+-------------+
*
*** EXTBK - Extent Block

EXTBK Cross Reference

Symbol         Dspl Value
-------------- ---- -----
EXTANYEX       0018
EXTEND         0008
EXTENSLT       0024
EXTFLAG        0031
EXTFREE        0028
EXTFULL        0031 80
EXTHIGH        0010
EXTINUSE       000C
EXTLOGEX       0031 20
EXTLOG1        0031 40
EXTMYEXT       001C
EXTPRPG        0032 0000004E
EXTSIZE        0032 00000007
EXTSIZEB       0032 00000034
EXTSLOTS       002C
EXTSTART       0004
EXTSTRCT       0014
EXTSTSLT       0020
EXTTYPE        0030
EXTVEXBK       0000