QDGBL | Back to Index page

| Prolog Control Block Contents QDGBL 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.

QDGBL Prolog | Top of page

     NAME       : Virtual Disk in Storage Global Control Block
     DESCRIPTION: V-Disk Global Control Block
     DSECT      : QDGBL
     FUNCTION   : This control block maps the global V-Disk
                  control block for the system.
     LOCATED BY : HCPSYSCM - System Common Area
     CREATED BY : HCPQDLIN
     DELETED BY : none
     SERIALIZED : QDGALOCK is used to serialize the QDGBL control block
                  fields.  QDGCLOCK is used to serialize the VDISK MDISK
                  chain (located by QDGMDISK).  Either QDGALOCK or
                  QDGCLOCK should be held shared when looking at the
                  VDISK MDISK chain.  Both must be held exclusive when
                  changing the VDISK MDISK chain.
     RELOCATION CONSIDERATIONS : None

QDGBL Control Block Content | Top of page

     QDGBL DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      QDGBL          V-Disk Global Control Block
                 Vdisk chain of MDISK blocks and allocation lockword
    0000    0 Dbl-Word     8 QDGALOCK (3)   Vdisk Allocation Lockword
    0018   24 Dbl-Word     8 QDGCLOCK (3)   Vdisk MDISK chain lock
    0030   48 Signed       4 QDGMDISK       First MDISK block for Vdisk
                 Fields for keeping track of limits (in blocks)
    0034   52 Signed       4 QDGSYSLM       Limit of total Vdisk allocation
    0038   56 Signed       4 QDGUSRLM       Limit of size of Vdisks DEFINEd
                                            by a user (using DEFINE)
    003C   60 Signed       4 QDGSYSCA       Total currently-allocated Vdisk
                                            blocks
    0040   64 Signed       4 QDGRELOC       Total relocation-allocated VDISK
                                            blocks
    0044   68 Signed       2 *              Reserved
    0046   70 Signed       2 QDGCOUNT       Vdisk counter for addr. space
                                            name (increment and save)
    0048   72 Signed       4 QDGLKCNT       Total number of LINKs to all
                                            Vdisks (includes 1 for each
                                            DEFINEd VDisk)
    004C   76 Signed       4 QDGDISKS       Total number of existing Vdisks
    0050   80 Signed       4 QDGSYSLD       Default of QDGSYSLM
    0054   84 Signed       4 QDGUSRLD       Default of QDGUSRLM
    0058   88 Bitstring    1 QDGAFLAG       'A' flag byte
              1... ....      QDGASYSC       X'80' QDGASYSC - SYSTEM CONFIG
                                            set syslim
    0059   89 Bitstring    1 * (3)          Reserved
              0000000C       QDGSIZE        ((*-QDGBL+7)/8) SIZE IN DWS FOR
                                            FREE/FRET

QDGBL Storage Layout | Top of page

    *** QDGBL - V-Disk Global Control Block
    *
    *     +-------------------------------------------------------+
    *   0 |                                                       |
    *     =                       QDGALOCK                        =
    *     |                                                       |
    *     +-------------------------------------------------------+
    *  18 |                                                       |
    *     =                       QDGCLOCK                        =
    *     |                                                       |
    *     +---------------------------+---------------------------+
    *  30 |         QDGMDISK          |         QDGSYSLM          |
    *     +---------------------------+---------------------------+
    *  38 |         QDGUSRLM          |         QDGSYSCA          |
    *     +---------------------------+-------------+-------------+
    *  40 |         QDGRELOC          |/////////////|  QDGCOUNT   |
    *     +---------------------------+-------------+-------------+
    *  48 |         QDGLKCNT          |         QDGDISKS          |
    *     +---------------------------+---------------------------+
    *  50 |         QDGSYSLD          |         QDGUSRLD          |
    *     +------+--------------------+---------------------------+
    *  58 |:AFLAG|////////////////////| 5C
    *     +------+--------------------+
    *
    *** QDGBL - V-Disk Global Control Block

QDGBL Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    QDGAFLAG       0058
    QDGALOCK       0000
    QDGASYSC       0058 80
    QDGCLOCK       0018
    QDGCOUNT       0046
    QDGDISKS       004C
    QDGLKCNT       0048
    QDGMDISK       0030
    QDGRELOC       0040
    QDGSIZE        0059 0000000C
    QDGSYSCA       003C
    QDGSYSLD       0050
    QDGSYSLM       0034
    QDGUSRLD       0054
    QDGUSRLM       0038

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:29:52 EDT.
Copyright IBM Corporation, 1990, 2020