STOBK | Back to Index page

| Prolog Control Block Contents STOBK 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.

STOBK Prolog | Top of page

     NAME       : DMSSTOBK
     DESCRIPTION: Storage descriptor block
     DSECT      : STOBK
     FUNCTION   : Mapping macro which maps allocated
                  and unallocated storage. There is a STOBK for
                  every page of storage within the virtual
                  machine.

STOBK Control Block Content | Top of page

     STOBK DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      STOBK          Storage descriptor block
    0000    0 Signed       4 STOFORWD       Forward pointer for chaining
                                            STOBKs
    0004    4 Signed       4 STOBACKW       Backward pointer for chaining
                                            STOBKs
          NOTES      : STOKEY and STOFLAG are often moved as a pair. This
                means that they must NEVER be seperated.
    0008    8 Signed       2 STOKFMOV (0)   For combined move of STOKEY and
                                            STOFLAG
    0008    8 Bitstring    1 STOKEY         Storage key for the described
                                            page
    0009    9 Bitstring    1 STOFLAG        Flags to define the described
                                            page
              1... ....      STOPAGE1       X'80' First STOBK on a block of
                                            STOBKs
              .1.. ....      STOBLOK1       X'40' First STOBK anchored on a
                                            SUBBK chain
              ...1 ....      STOFLPT        X'10' Page is a full-partial
                                            (only valid when STOPART flag is
                                            on)
              .... 1...      STORELPG       X'08' Page has not been released
                                            to CP via DIAG X'10'
              .... .1..      STOINTRN       X'04' Page is internal CMS
                                            Storage
              .... ..1.      STOFULL        X'02' Page is fully allocated
              .... ...1      STOPART        X'01' Page is partially allocated
    000A   10 Signed       2 STOLARGE       Size of the largest free piece in
                                            a page
    000C   12 Signed       4 STOFREEB (0)   Anchor to the free pieces in a
                                            page
    000C   12 Signed       4 STOFIRST (0)   Pointer to the first STOBK on a
                                            block
    000C   12 Signed       4 STONUMBL       Number of pages on a block
    0010   16 Signed       4 STOSUBAD       Pointer to the SUBBK for this
                                            STOBK
    0014   20 Signed       4 *              IBM Reserved
              00000018       STOSIZEB       *-STOBK Size of a STOBK in bytes
              00000003       STOSIZED       (STOSIZEB+7)/8 Size of a STOBK in
                                            D-words

STOBK Storage Layout | Top of page

    *** STOBK - Storage descriptor block
    *
    *     +---------------------------+---------------------------+
    *   0 |         STOFORWD          |         STOBACKW          |
    *     +------+------+-------------+---------------------------+
    *   8 |STOKEY|:FLAG |  STOLARGE   |         STONUMBL          |
    *     +------+------+-------------+---------------------------+
    *  10 |         STOSUBAD          |///////////////////////////|
    *     +---------------------------+---------------------------+
    *  18
    *
    *** STOBK - Storage descriptor block

STOBK Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    STOBACKW       0004
    STOBLOK1       0009 40
    STOFIRST       000C
    STOFLAG        0009
    STOFLPT        0009 10
    STOFORWD       0000
    STOFREEB       000C
    STOFULL        0009 02
    STOINTRN       0009 04
    STOKEY         0008
    STOKFMOV       0008
    STOLARGE       000A
    STONUMBL       000C
    STOPAGE1       0009 80
    STOPART        0009 01
    STORELPG       0009 08
    STOSIZEB       0014 00000018
    STOSIZED       0014 00000003
    STOSUBAD       0010

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:36:19 EDT.
Copyright IBM Corporation, 1990, 2020