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 DSECT
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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 - 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.

 
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