ACABK | Back to Index page

| Prolog Control Block Contents ACABK 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.

ACABK Prolog | Top of page

     NAME       : HCPVEXBK
     DESCRIPTION: Map CASBKs at beginning of VEXBK.
     DSECT      : ACABK
     NOTES      : The following maps the area at the beginning of the
                  VEXBK which contains the CASBKs.  Hence, this DSECT
                  is called the ACABK (Area for Contiguous Available
                  Slots).  The ACABK is used to avoid checking for
                  page or spool slots numerous times.

ACABK Control Block Content | Top of page

     ACABK DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      ACABK          Map CASBKs at beginning of VEXBK.
    0000    0 Signed       4 ACACAS (16)    Contains 16 CASBKS used by slot
                                            allocation.
    0040   64 Signed       4 ACACURSL       Current slot number in EXTBK
                                            (start search for new CASBK here)
    0044   68 Signed       4 ACALSTSL       Last slot in current cylinder
    0048   72 Signed       4 ACACURCY       Current cylinder in EXTBK
    004C   76 Signed       4 ACAEXTBK       Pointer to current EXTBK
    0050   80 Bitstring    1 ACAFIRST       Index into ACABK of first CASBK
    0051   81 Bitstring    1 ACALAST        Index into ACABK of last CASBK
    0052   82 Bitstring    1 ACAFLAG        Flags
              1... ....      ACAREDO        X'80' ACAREDO Slots were
                                            allocated by a method other than
                                            slot alloc. (PGC or PGTDA) Redo
                                            CASBKs before slot allocation.
              .1.. ....      ACAANYRP       X'40' ACAANYRP No minimum size
                                            when searching for a replacement
                                            CASBK. (space is fragmented)
              ..1. ....      ACAANYAL       X'20' ACAANYAL Take any size
                                            CASBK when searching for a block
                                            for allocation. (this is set
                                            temporarily for large block
                                            requests)
              ...1 ....      ACAINIT        X'10' ACAINIT CASBKs have been
                                            initialized
    0053   83 Bitstring    1 * (5)          Reserved for IBM use
              00000058       ACASIZE        *-ACABK Size of area for CASBKs.

ACABK Storage Layout | Top of page

    *** ACABK - Map CASBKs at beginning of VEXBK.
    *
    *     +-------------------------------------------------------+
    *   0 |                                                       |
    *     =                        ACACAS                         =
    *     |                                                       |
    *     +---------------------------+---------------------------+
    *  40 |         ACACURSL          |         ACALSTSL          |
    *     +---------------------------+---------------------------+
    *  48 |         ACACURCY          |         ACAEXTBK          |
    *     +------+------+------+------+---------------------------+
    *  50 |:FIRST|:LAST |:FLAG |//////////////////////////////////|
    *     +------+------+------+----------------------------------+
    *  58
    *
    *** ACABK - Map CASBKs at beginning of VEXBK.

ACABK Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    ACAANYAL       0052 20
    ACAANYRP       0052 40
    ACACAS         0000
    ACACURCY       0048
    ACACURSL       0040
    ACAEXTBK       004C
    ACAFIRST       0050
    ACAFLAG        0052
    ACAINIT        0052 10
    ACALAST        0051
    ACALSTSL       0044
    ACAREDO        0052 80
    ACASIZE        0053 00000058

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:31:35 EDT.
Copyright IBM Corporation, 1990, 2020