NAME       : HCPPHDBK
 DESCRIPTION: Paging Information Header Block
 DSECT      : PHDBK
 FUNCTION   : The paging information header block maps
              information at the beginning of a paging
              exposure block (EXPBK) or Hyperpav paging block
              (HXPBK).
 LOCATED BY : EXPPHDBK - Points to area within an EXPBK that
              is mapped by a PHDBK
              HXPPHDBK - Points to area within an HXPBK that
              is mapped by a PHDBK
 CREATED BY : Not explicitly created
 DELETED BY : Not explicitly deleted
 SERIALIZED :
              Serialization of fields mapped by this control
              block vary.  See line comments on each field for
              specifics.
 RELOCATION CONSIDERATIONS : None
 COMMENTS   :

 PHDBK DSECT
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Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      PHDBK          Paging Information Header Block
0000    0 Character    8 PHDEYE         Eyecatcher HCPHXPBK or HCPEXPBK
0008    8 Bitstring    1 PHDTYPEF       Flag byte for access type. Used
                                        directly by Perfkit. Do not
                                        change offset. Task
                                        serialization.
          1... ....      PHDHXPBK       X'80' Indicates area being mapped
                                        is within an HXPBK; when bit is
                                        0, area mapped is within an EXPBK
          .1.. ....      PHDECKD        X'40' ECKD device
          ..1. ....      PHDSCSI        X'20' Native SCSI device (EXPBK
                                        only)
          ...1 ....      PHDFBA         X'10' FBA device
0009    9 Bitstring    1 * (3)          Reserved for IBM use
000C   12 Signed       4 *              Reserved for IBM use
      Monitor counts of read and write operations for this device
0010   16 Dbl-Word     8 * (0)          Alignment
0010   16 Signed       4 PHDCTPRD       Total count of page reads. Used
                                        directly by Perfkit. Do not
                                        change offset. Compare & Swap to
                                        update.
0014   20 Signed       4 PHDCTPWR       Total count of page writes Used
                                        directly by Perfkit. Do not
                                        change offset. Compare & Swap to
                                        update.
0018   24 Signed       4 PHDCTSRD       Total count of spooling reads
                                        Used directly by Perfkit. Do not
                                        change offset. Compare & Swap to
                                        update.
001C   28 Signed       4 PHDCTSWR       Total count of spooling writes
                                        Used directly by Perfkit. Do not
                                        change offset. Compare & Swap to
                                        update.
0020   32 Signed       4 PHDSSCHR       Total count of SSCHs (or RSCHs
                                        when EXPBK) for read. Used
                                        directly by Perfkit. Do not
                                        change offset. Task
                                        serialization.
0024   36 Signed       4 PHDSSCHW       Total count of SSCHs (or RSCHs
                                        when EXPBK) for write. Used
                                        directly by Perfkit. Do not
                                        change offset. Task
                                        serialization.
0028   40 Signed       4 PHDLOCRR       Total count of Locate Record
                                        operations for read (includes the
                                        initial search even when the
                                        information is provided by a
                                        Prefix CCW). Used directly by
                                        Perfkit. Do not change offset.
                                        Task serialization.
002C   44 Signed       4 PHDLOCRW       Total count of Locate Record
                                        operations for write (includes
                                        the initial search even when the
                                        information is provided by a
                                        Prefix CCW). Used directly by
                                        Perfkit. Do not change offset.
                                        Task serialization.
      Device service time and MLOAD fields
0030   48 Dbl-Word     8 * (0)          Alignment
0030   48 Signed       4 PHDDEVST       Device service time. In EXPBK,
                                        serialized by EXPLCKFG. In PHDBK,
                                        serialized by HXPC1LCK. Used
                                        directly by Perfkit. Do not
                                        change offset. Compare & Swap to
                                        update.
0034   52 Signed       4 PHDMLOAD       MLOAD. Serialized by HCPPGDML.
                                        Used directly by Perfkit. Do not
                                        change offset.
      Slot allocation
0038   56 Dbl-Word     8 * (0)          Alignment
0038   56 Signed       4 PHDCONT (20)   Array of 20 fullword slot
                                        allocation counters. The count at
                                        index (i) is incremented each
                                        time a block with (i) contiguous
                                        slots is allocated. The last
                                        count in the array is also
                                        incremented when a block w/
                                        >20 slots is allocated. Used
                                        directly by Perfkit. Do not
                                        change offset. Serialization is
                                        HCPPGDPL for a paging volume, and
                                        HCPPGDSL for a spool volume.
                                        Accuracy of these counters depend
                                        on volume usage not being mixed
                                        page and spool as per
                                        recommendations.
0088  136 Address      4 PHDRDCBK       Pointer to RDCBK which contains
                                        device/control unit information
                                        Task serialization.
008C  140 Signed       4 *              Reserved for IBM use.
      Reserved area
      If there is a need in the service stream to add additional
      fields to the PHDBK, the following reserved area should be
      used to avoid changing offsets of EXPBK fields and
      recompiles to all of the legacy paging code.
      Lengthening the PHDBK (up to 256 bytes) does not have the
      same consideration for the HXPBK because the PHDBK is in its
      own HXPBK cache line.
0090  144 Dbl-Word     8 * (4)          Reserved for IBM use.
          000000B0       PHDBSIZE       *-PHDBK Size of this DSECT in
                                        Bytes
          00000016       PHDSIZE        (((*-PHDBK)+7)/8) Size in
                                        double-words

          
*** PHDBK - Paging Information Header Block
*
*     +-------------------------------------------------------+
*   0 |                        PHDEYE                         |
*     +------+--------------------+---------------------------+
*   8 |:TYPEF|////////////////////|///////////////////////////|
*     +------+--------------------+---------------------------+
*  10 |         PHDCTPRD          |         PHDCTPWR          |
*     +---------------------------+---------------------------+
*  18 |         PHDCTSRD          |         PHDCTSWR          |
*     +---------------------------+---------------------------+
*  20 |         PHDSSCHR          |         PHDSSCHW          |
*     +---------------------------+---------------------------+
*  28 |         PHDLOCRR          |         PHDLOCRW          |
*     +---------------------------+---------------------------+
*  30 |         PHDDEVST          |         PHDMLOAD          |
*     +---------------------------+---------------------------+
*  38 |                                                       |
*     =                       PHDCONT                         =
*     |                                                       |
*     +---------------------------+---------------------------+
*  88 |         PHDRDCBK          |///////////////////////////|
*     +---------------------------+---------------------------+
*  90 |///////////////////////////////////////////////////////|
*     =///////////////////////////////////////////////////////=
*     |///////////////////////////////////////////////////////|
*     +-------------------------------------------------------+
*  B0
*
*** PHDBK - Paging Information Header Block

 
Symbol         Dspl Value
-------------- ---- -----
PHDBSIZE       0090 000000B0
PHDCONT        0038
PHDCTPRD       0010
PHDCTPWR       0014
PHDCTSRD       0018
PHDCTSWR       001C
PHDDEVST       0030
PHDECKD        0008 40
PHDEYE         0000
PHDFBA         0008 10
PHDHXPBK       0008 80
PHDLOCRR       0028
PHDLOCRW       002C
PHDMLOAD       0034
PHDRDCBK       0088
PHDSCSI        0008 20
PHDSIZE        0090 00000016
PHDSSCHR       0020
PHDSSCHW       0024
PHDTYPEF       0008