STLBK | Back to Index page

| Prolog Control Block Contents STLBK 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.

STLBK Prolog | Top of page

     NAME       : HCPSTLBK
     DESCRIPTION: SEGMENT TABLE ENTRY LIST BLOCK
     DSECT      : STLBK
     FUNCTION   : THERE IS A SEGMENT TABLE ENTRY LIST BLOCK FOR
                  EACH ACTIVE NAMED SAVED SYSTEM (NSS)
                  OR DISCONTIGUOUS SAVED SEGMENT (DCSS).
                  Within the block there are pointers to the STLTEs
                  for each megabyte of address space in the NSS or
                  DCSS.  STLTEs are packaged in sets of up to
                  "STLTEper", each set in a separate block.
                  STLSTEPT points to the 1st block of STLTEs.
                  Subsequent pointers point to additional blocks
                  of STLTEs.
                  These STLTEs are mapped by HCPSTLTE COPY and
                  the STLTE DSECT.
                  The number of segments determines how much
                  storage will be allocated to contain the STLTEs.
                  THE SEGMENTS CAN BE SHARED OR EXCLUSIVE.
     LOCATED BY : SNTSTLPT  FIELD OF HCPSNTBK
     CREATED BY : HCPBSCBS - Build Segment Space STLBK
                  HCPBSCSL  WHEN AT NSS OR DCSS IS FIRST REFERENCED
                  AN STLBK IS ATTACHED TO THE USER VIA AN IMBED OPERATION.
                  ENTRY POINT HCPBSIIM PERFORMS IMBED OPERATIONS.
     DELETED BY : HCPUIMSL  WHEN A NSS OR DCSS IS NO LONGER ACTIVE.
                  AN STLBK IS DETACHED FROM THE USER VIA A REMOVE OPERATION.
                  MODULE HCPUIMRM PERFORMS REMOVE OPERATIONS.
     RELOCATION CONSIDERATIONS : None

STLBK Control Block Content | Top of page

     STLBK DSECT
    Top of page

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      STLBK          SEGMENT TABLE ENTRY LIST BLOCK
    0000    0 Signed       2 STLSTECT       Number of STLTEs for NSS/DCSS.
    0002    2 Signed       2 *              Reserved for HCPBSC exclusively.
                                            HCPBSC builds STLBKs. As the
                                            builder, HCPBSC has exclusive
                                            access to the STLBK.
                                      During the building of
                                      STLBKs, HCPBSC may be
                                      manipulating more than 1
                                      STLBK at a time, and so may
                                      need more than 1 "index to
                                      current STLTE" field.  It is
                                      convenient to place the
                                      fields with their respective
                                      STLBKs.
                                      However, after the STLBK is
                                      built and made available,
                                      there may be more than 1 task
                                      touching the same STLBK.  In
                                      such cases, the "index" must
                                      not be in the STLBK because
                                      the tasks will be updating
                                      the "index" for their own
                                      needs, so each task must have
                                      its own "index" field.
    0004    4 Address      4 STLSTEPT       Addresses of blocks filled with
                                            STLTEs. STLTEs point to page
                                            tables within PGMBKs. The STLTE
                                            is mapped by the HCPSTLTE COPY
                                            file.
                                      STLSTEPT points to the first
                                      STLTE.
          Areas for STLTEs are allocated dynamically, and the
          pointers to those areas are stored in STLSTEPT, and
          subsequent positions in storage.  The number of such
          areas, and the number of pointers to point to those
          areas, is determined by the maximum number of STLTEs
          (2048) and the maximum number of STLTEs per area
          (STLTEper).   STLnofPT will be calculated from these
          numbers, and sufficient pointers will be reserved.
              00000004       STLnofPT       (2048/STLTEper) nof pointers
                                            needed
    0008    8 Address      4 * (3)          STLSTEPT already has one. This
                                            reserves the rest.
              00000003       STLSIZE        (*-STLBK+7)/8 STLBK SIZE IN
                                            DOUBLEWORDS

STLBK Storage Layout | Top of page

    *** STLBK - SEGMENT TABLE ENTRY LIST BLOCK
    *
    *     +-------------+-------------+---------------------------+
    *   0 |  STLSTECT   |/////////////|         STLSTEPT          |
    *     +-------------+-------------+---------------------------+
    *   8 |///////////////////////////////////////////////////////|
    *     |///////////////////////////+---------------------------+
    *     |///////////////////////////| 14
    *     +---------------------------+
    *
    *** STLBK - SEGMENT TABLE ENTRY LIST BLOCK

STLBK Cross Reference | Top of page

    Symbol         Dspl Value
    -------------- ---- -----
    STLnofPT       0004 00000004
    STLSIZE        0008 00000003
    STLSTECT       0000
    STLSTEPT       0004

This information is based on z/VM 7.2.0 Last updated on 24 Jun 2020 at 09:31:05 EDT.
Copyright IBM Corporation, 1990, 2020