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 DELETED BY : HCPUIMSL  WHEN A NSS OR DCSS IS NO LONGER ACTIVE.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