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| Prolog Control Block Contents DSCBK 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.

DSCBK Prolog | Top of page

     NAME       : HCPDSCBK
     DESCRIPTION: Demand Scan Control Block
     DSECT      : DSCBK
     FUNCTION   :
                  The Demand Scan Control Block (DSCBK) contains
                  information about the Available List Demand Scan
                  operation.  The DSCBK is persistent and some
                  information is saved between Demand Scans.
     CREATED BY : Assembly at Entry Point HCPRSMSC.
     DELETED BY : none
     RELOCATION CONSIDERATIONS : None

DSCBK Control Block Content | Top of page

     DSCBK DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      DSCBK          Demand Scan Control Block
    0000    0 Signed       4 *              Reserved for IBM use
    0004    4 Signed       4 DSCINPUT (0)   Demand Scan Input Word DSCINPUT
                                            is a word of "input status" hints
                                            for other parts of the system to
                                            communicate information "hints"
                                            to demand scan. NOTES : DSCINPUT
                                            fields are NOT serialized, by the
                                            demand scan lock or anything
                                            else.
    0004    4 Bitstring    1 *              Reserved
          The following bytes are used to make sure that only
          one CPEBK is stacked for a deferred call to various places.
    0005    5 Bitstring    1 *              Reserved
    0006    6 Bitstring    1 DSCFMVLK       Indicate that the deferred call
                                            to HCPFMVDS has been stacked
    0007    7 Bitstring    1 *              Reserved
    0008    8 Bitstring    1 *              reserved
    0009    9 Bitstring    1 DSCALRDS       A deferred call to HCPALRDS is
                                            either stacked or running
    000A   10 Bitstring    1 * (6)          reserved
    0010   16 Signed       4 DSCCYCL        Count the number of scan cycles
    0014   20 Signed       4 *              Reserved
          These fields apply to the current Demand Scan.
    0018   24 Signed       4 * (2)          Reserved Output from subroutine
                                            CALCMORE in HCPALU. Updated by
                                            CALCMORE. Not changed until the
                                            next call to CALCMORE. These are
                                            "type-any" needs and represent a
                                            current need. (I.E. Deficit
                                            numbers are not factored in.)
    0020   32 Dbl-Word     8 DSCREQSingles  Singles Frames needed.
    0028   40 Dbl-Word     8 DSCREQContigs  Contigs Frames needed.
    0030   48 Dbl-Word     8 DSCSTLW (0)    Steal Write counters (Low/High)
    0030   48 Signed       4 DSCSTLW0       Steal Write frames BELOW 2Gb
    0034   52 Signed       4 DSCSTLWG       Steal Write frames 2Gb and ABOVE
    0038   56 Signed       4 DSCSTLP0       Steal Write PGMBKs BELOW 2Gb
    003C   60 Signed       4 DSCSTLPG       Steal Write PGMBKs 2Gb and ABOVE
              00000010       DSCSTLWL       *-DSCSTLW Length of all STL
                                            fields
    0040   64 Signed       8 * (6)          Reserved for IBM use
    0070  112 Signed       4 *              Reserved for IBM use
          These fields are primarily for diagnostic purposes.
          They should not affect the operation of Demand Scan.
    0074  116 Bitstring    1 DSCDEBUG       Debug Flags
              1... ....      DSCACTIV       X'80' DSCACTIV Demand Scan is
                                            ACTIVE
    0075  117 Bitstring    3 *              reserved
    0078  120 Signed       4 DSCCOUNT       Count the number of times we
                                            entered Demand Scan (HCPALDSC)
    007C  124 Signed       4 *              Reserved
    0080  128 Signed       4 *              Reserved
    0084  132 Address      4 DSCWHOEX       Previous HCPCALL before CALCMORE
    0088  136 Signed       4 *              Reserved
    008C  140 Signed       4 *              Reserved
    0090  144 Signed       8 * (4)          Reserved for IBM use
    00B0  176 Signed       4 *              Reserved for IBM use
    00B4  180 Signed       4 DSCALSKF       Times an Aging List page was not
                                            taken (i.e. was skipped) because
                                            we couldn't get frame ser.
    00B8  184 Signed       4 DSCALSKP       Times an Aging List page was not
                                            taken (i.e. was skipped) because
                                            we couldn't get PTE serializ.
    00BC  188 Signed       4 *              Reserved
    00C0  192 Signed       4 *              Reserved
    00C4  196 Signed       4 *              Reserved
          Communication from the frame manager to subroutine CALCMORE.
    00C8  200 Dbl-Word     8 DSCRSingles    (Rate) Need for type any singles.
    00D0  208 Dbl-Word     8 DSCRContigs    (Rate) Need for type any contigs.
          CALCMORE data area.
          These values represent harvested rate based information.
          Not technically output, but only used for Demand scan calls.
    00D8  216 Dbl-Word     8 DSCHSingles    (Rate) Harvested need for
                                            singles.
    00E0  224 Dbl-Word     8 DSCHContigs    (Rate) Harvested need for
                                            contigs.
          These values are the rate based need to use for the current
          call to CALCMORE.  (Either DSCHSingles at the beginning of
          a new Demand scan.   Or a Delta at the end of a Demand scan.)
          Not technically output, but only used for Demand scan calls.
    00E8  232 Dbl-Word     8 DSCNSingles    Rate based need for singles.
    00F0  240 Dbl-Word     8 DSCNContigs    Rate based need for contigs.
          "Who invoked demand scan" data:
    00F8  248 Signed       4 DSCwhoFg (0)
    00F8  248 Bitstring    1 DSCwhoRq       Who invoked demand scan (debug
                                            only build) - all requestors
    00F9  249 Bitstring    1 DSCwhoFl       Who invoked demand scan (debug
                                            only build) - who actually
                                            flagpoled
          Equates for DSCwhoRq and DSCwhoFl
              1... ....      DSCwhoDSEW     X'80' 1 ALG DSEarlyWrite
              .1.. ....      DSCwhoDSRS     X'40' 2 ALDSC DSRestart
              ..1. ....      DSCwhoTHRS     X'20' 3 ALUDS Threshold
              ...1 ....      DSCwhoAGRV     X'10' 4 PFR AgingRevals
              .... 1...      DSCwhoFRDF     X'08' 5 PTF FrameReqDefer
              .... .1..      DSCwhoLGR      X'04' 6 RLT LGR EQU X'02' 7
                                            Unused.
              .... ...1      DSCwhoAgIn     X'01' 8 ALUDS AgeSizeInc
    00FA  250 Bitstring    1 * (2)          Reserved for DSCwhoFg expansion,
                                            must remain 0s
          Array of counts of times each task attempted to flag Demand
          scan to start:
    00FC  252 Signed       4 DSCwhoCtArray (8)
                                            (debug only build)
    00FC  252 Signed       4 DSCwhoCtDSEW   1 ALG DSEarlyWrite
    0100  256 Signed       4 DSCwhoCtDSRS   2 ALDSC DSRestart
    0104  260 Signed       4 DSCwhoCtTHRS   3 ALUDS DSThreshold
    0108  264 Signed       4 DSCwhoCtAGRV   4 PFR AgingRevals
    010C  268 Signed       4 DSCwhoCtFRDF   5 PTF FrameReqDefer
    0110  272 Signed       4 DSCwhoCtLGR    6 RLT LGR
    0114  276 Signed       4 *              7 Unused.
    0118  280 Signed       4 DSCwhoCTAgIn   8 ALUDS AgeSizeInc
    011C  284 Bitstring    1 DSC$END (0)    End of DSCBK
              0000011C       DSCBKLN        *-DSCBK DSCBK length (in bytes)
              00000024       DSCBKSZ        (*-DSCBK+7)/8 DSCBK size (in
                                            doublewords)

DSCBK Storage Layout | Top of page

    *** DSCBK - Demand Scan Control Block
    *
    *     +---------------------------+------+------+------+------+
    *   0 |///////////////////////////|//////|//////|:FMVLK|//////|
    *     +------+------+-------------+------+------+------+------+
    *   8 |//////|:ALRDS|/////////////////////////////////////////|
    *     +------+------+-------------+---------------------------+
    *  10 |         DSCCYCL           |///////////////////////////|
    *     +---------------------------+---------------------------+
    *  18 |///////////////////////////////////////////////////////|
    *     +-------------------------------------------------------+
    *  20 |                    DSCREQSINGLES                      |
    *     +-------------------------------------------------------+
    *  28 |                    DSCREQCONTIGS                      |
    *     +---------------------------+---------------------------+
    *  30 |         DSCSTLW0          |         DSCSTLWG          |
    *     +---------------------------+---------------------------+
    *  38 |         DSCSTLP0          |         DSCSTLPG          |
    *     +---------------------------+---------------------------+
    *  40 |///////////////////////////////////////////////////////|
    *     =///////////////////////////////////////////////////////=
    *     |///////////////////////////////////////////////////////|
    *     +---------------------------+------+--------------------+
    *  70 |///////////////////////////|:DEBUG|////////////////////|
    *     +---------------------------+------+--------------------+
    *  78 |         DSCCOUNT          |///////////////////////////|
    *     +---------------------------+---------------------------+
    *  80 |///////////////////////////|         DSCWHOEX          |
    *     +---------------------------+---------------------------+
    *  88 |///////////////////////////|///////////////////////////|
    *     +---------------------------+---------------------------+
    *  90 |///////////////////////////////////////////////////////|
    *     =///////////////////////////////////////////////////////=
    *     |///////////////////////////////////////////////////////|
    *     +---------------------------+---------------------------+
    *  B0 |///////////////////////////|         DSCALSKF          |
    *     +---------------------------+---------------------------+
    *  B8 |         DSCALSKP          |///////////////////////////|
    *     +---------------------------+---------------------------+
    *  C0 |///////////////////////////|///////////////////////////|
    *     +---------------------------+---------------------------+
    *  C8 |                     DSCRSINGLES                       |
    *     +-------------------------------------------------------+
    *  D0 |                     DSCRCONTIGS                       |
    *     +-------------------------------------------------------+
    *  D8 |                     DSCHSINGLES                       |
    *     +-------------------------------------------------------+
    *  E0 |                     DSCHCONTIGS                       |
    *     +-------------------------------------------------------+
    *  E8 |                     DSCNSINGLES                       |
    *     +-------------------------------------------------------+
    *  F0 |                     DSCNCONTIGS                       |
    *     +------+------+-------------+---------------------------+
    *  F8 |:WHORQ|:WHOFL|/////////////|                           |
    *     +------+------+-------------+                           |
    * 100 |                                                       |
    *     =                    DSCWHOCTARRAY                      =
    *     |                           +---------------------------+
    *     |                           | 11C
    *     +---------------------------+
    *
    *** DSCBK - Demand Scan Control Block

    *** Overlay for DSCwhoCtArray in DSCBK
    *
    *                                 +---------------------------+
    *  F8 ...                      FC |       DSCWHOCTDSEW        |
    *     +---------------------------+---------------------------+
    * 100 |       DSCWHOCTDSRS        |       DSCWHOCTTHRS        |
    *     +---------------------------+---------------------------+
    * 108 |       DSCWHOCTAGRV        |       DSCWHOCTFRDF        |
    *     +---------------------------+---------------------------+
    * 110 |       DSCWHOCTLGR         |///////////////////////////|
    *     +---------------------------+---------------------------+
    * 118 |       DSCWHOCTAGIN        |
    *     +---------------------------+
    *
    *** Overlay for DSCwhoCtArray in DSCBK

DSCBK Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    DSC$END        011C
    DSCwhoAgIn     00F9 01
    DSCwhoAGRV     00F9 10
    DSCwhoCtArray  00FC
    DSCwhoCtAGRV   0108
    DSCwhoCtDSEW   00FC
    DSCwhoCtDSRS   0100
    DSCwhoCtFRDF   010C
    DSCwhoCtLGR    0110
    DSCwhoCtTHRS   0104
    DSCwhoCTAgIn   0118
    DSCwhoDSEW     00F9 80
    DSCwhoDSRS     00F9 40
    DSCwhoFg       00F8
    DSCwhoFl       00F9
    DSCwhoFRDF     00F9 08
    DSCwhoLGR      00F9 04
    DSCwhoRq       00F8
    DSCwhoTHRS     00F9 20
    DSCACTIV       0074 80
    DSCALRDS       0009
    DSCALSKF       00B4
    DSCALSKP       00B8
    DSCBKLN        011C 0000011C
    DSCBKSZ        011C 00000024
    DSCCOUNT       0078
    DSCCYCL        0010
    DSCDEBUG       0074
    DSCFMVLK       0006
    DSCHContigs    00E0
    DSCHSingles    00D8
    DSCINPUT       0004
    DSCNContigs    00F0
    DSCNSingles    00E8
    DSCRContigs    00D0
    DSCREQContigs  0028
    DSCREQSingles  0020
    DSCRSingles    00C8
    DSCSTLPG       003C
    DSCSTLP0       0038
    DSCSTLW        0030
    DSCSTLWG       0034
    DSCSTLWL       003C 00000010
    DSCSTLW0       0030
    DSCWHOEX       0084

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:27:52 EDT.
Copyright IBM Corporation, 1990, 2020