PHDBK | Back to Index page

| Prolog Control Block Contents PHDBK 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.

PHDBK Prolog | Top of page

     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 Control Block Content | Top of page

     PHDBK DSECT
    Top of page

    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 Storage Layout | Top of page

    *** 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

PHDBK Cross Reference | Top of page

    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

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:29:39 EDT.
Copyright IBM Corporation, 1990, 2020