PGAUX | Back to Index page

| Prolog Control Block Contents PGAUX 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.

PGAUX Prolog | Top of page

     NAME       : PGAUX
     DESCRIPTION: Page Auxiliary Status Table Entry
     DSECT      : PGAUX
     FUNCTION   : Auxiliary extension of the PGSTE
                  PGAUX is a multi-purpose area:
                  - When PGSTE.PGSOVFLW=1, then PGAUX contains
                  an overflow pin count.
                  - When a page is IBR (PGSTE.PGSIBR=1 or
                  PGSTE.PGSAGING=1), then PGAUX contains
                  a portion of a timestamp used to record
                  IBR state changes.
                  It is the developer's responsibility to ensure
                  residual data is cleared from PGAUX before
                  repurposing the field.
     LOCATED BY : PGMGPAUX  Field of HCPPGMBK + PTE offset / 2
                  A page auxiliary status table resides in a
                  page management block associated with a megabyte
                  of virtual storage and is addressed by label
                  PGMGPAUX.  There are 256 contiguous page auxiliary
                  status table entries (PGAUXs) contained in the
                  PGMBK.
                  Any specific aux table entry can be obtained by
                  extracting the page index from a virtual address,
                  multiplying it by the length of an aux entry, and
                  adding this offset to the start of the page status
                  table.  Also, using the address of a PAGTE as the
                  address of a VPGBK, the corresponding PGAUX can be
                  found by calculating the offset of the PTE from the
                  page table origin, dividing by two, and adding the
                  resulting word offset to the start of the page
                  auxiliary status table.
                  Utility macro HCPPTEAX can be used to fetch and
                  modify the PGAUX area for a specific PTE.
     CREATED BY : A page status aux table is imbedded in a page
                  management block.  Consequently, space is created
                  for it when the PGMBK is created.
     DELETED BY : HCPHPKPA
                  A page status aux table is deleted when a page
                  management block is released.
     SERIALIZED :
                  Serialized by PTE/PGSTE serialization, either
                  Shortterm or PCLONLY.
     RELOCATION CONSIDERATIONS : None

PGAUX Control Block Content | Top of page

     PGAUX DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      PGAUX          Page Auxiliary Status Table Entry
    0000    0 Signed       4 PGAUXENT (0)   Aux entry
    0000    0 Signed       2 *              Reserved for IBM use
    0002    2 Signed       2 PGAOVFLW       Overflow pin count Count of the
                                            number of 128 pin- count overflow
                                            increments. Each increment of
                                            ASAOVFLW represents 128 pins. The
                                            pin count for a page is kept in
                                            PGSPINCT, which is only 1 byte in
                                            length and can hold up to 127 pin
                                            increments. If that overflows,
                                            ASAOVFLW is incremented and
                                            therefore represents 128 pins.
                                            Note that ASAOVFLW can be changed
                                            with PCLONLY page serialization
                                            by those tasks that are allowed
                                            to use PCLONLY.

PGAUX Storage Layout | Top of page

    *** PGAUX - Page Auxiliary Status Table Entry
    *
    *     +-------------+-------------+
    *   0 |/////////////|  PGAOVFLW   | 4
    *     +-------------+-------------+
    *
    *** PGAUX - Page Auxiliary Status Table Entry

PGAUX Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    PGAOVFLW       0002
    PGAUXENT       0000

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:31:40 EDT.
Copyright IBM Corporation, 1990, 2020