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 7.3.0 Last updated on 22 Jun 2022 at 15:53:36 EDT.
Copyright IBM Corporation, 1990, 2022