ALCBK Back to Index page
 
Prolog 
Control Block Contents 
   ALCBK 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.


  ALCBK Prolog Top of page
 
 NAME       : HCPALCBK
 DESCRIPTION: Access-List Control Block
 DSECT      : ALCBK
 FUNCTION   : This DSECT maps the control block used to manage an
              ESA/370 access list.
 LOCATED BY : ALEALCBK in the second access-list entry of an access
              list built by CP (the one with ALEN=1).
 CREATED BY : HCPALMCR when an access list is created.
 DELETED BY : HCPALMDS when an access list is destroyed.
 RELOCATION CONSIDERATIONS : None
 NOTES      : Serialization of the access-list depends on whether the
              list is the CP-use access list, or a guest-use access
              list:
              For the CP-use access list:
              - An ALE is validated using CDSG.
              - If no ALE is available, the ATTACH task is
              suspended to await an available entry.  The
              queue of deferred tasks is anchored in ALCDEFRQ.
              - The deferred task at the head of the queue is
              driven on a subsequent DETACH.
              - ALCDEFRQ and ALCFREE (count of available ALEs)
              are in the same doubleword, and are modified
              using CSG.  This technique closes a window where
              an ATTACH task is in the process of deferring,
              while a DETACH is in progress.
              - Since multiple tasks can be deferred, the
              ALCLOCK is obtained when manipulating the
              ALCDEFRQ queue.
              For a guest-use access list:
              - The ALCLOCK controls all changes to the ALCBK.
 
 
  ALCBK Control Block Content Top of page
 

 ALCBK DSECT Top of page
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure ALCBK Access-List Control Block block. 0000 0 Address 4 ALCALD Address of access-list designation. 0004 4 Address 4 ALCAL Address of access list 0008 8 Address 4 ALCOWNER Address of VMDBK which owns the access list. 000C 12 Signed 4 * Reserved for IBM use 0010 16 Address 4 ALCSPIBK Anchor for chain of SPIBKs defining what address spaces may be attached to this access list. This is serialized by the space-permission-manager lock (RSASPMLK in HCPRSMCM). 0014 20 Signed 4 * Reserved for IBM use. 0018 24 Dbl-Word 8 ALCLOCK (3) Lockword for access-list-control lock. 0030 48 Signed 4 ALCALSIZ Size of access list, in bytes. 0034 52 Signed 4 ALCMAXSZ Largest permitted size of access list, in bytes. 0038 56 Signed 8 ALCCSDWD (0) Queue hdr and available count. Serialized with CSG for the CP-use access list. See ALCBK prolog for details. 0038 56 Address 4 ALCDEFRQ Anchor for queue of tasks adding entries to the CP-use AL which have been deferred because the CP-use access list is full. 003C 60 Signed 4 ALCFREE Number of ALEs in the invalid state (not including ALENs 0 and 1). This is the number of ALEs available for allocation. 00000040 ALCLEN *-ALCBK Length in bytes of ALCBK. 00000008 ALCSIZE (ALCLEN+7)/8 Size in doublewords of an ALCBK
 
 
  ALCBK Storage Layout Top of page
 
          
*** ALCBK - Access-List Control Block
*
*     +---------------------------+---------------------------+
*   0 |          ALCALD           |          ALCAL            |
*     +---------------------------+---------------------------+
*   8 |         ALCOWNER          |///////////////////////////|
*     +---------------------------+---------------------------+
*  10 |         ALCSPIBK          |///////////////////////////|
*     +---------------------------+---------------------------+
*  18 |                                                       |
*     =                       ALCLOCK                         =
*     |                                                       |
*     +---------------------------+---------------------------+
*  30 |         ALCALSIZ          |         ALCMAXSZ          |
*     +---------------------------+---------------------------+
*  38 |         ALCDEFRQ          |         ALCFREE           |
*     +---------------------------+---------------------------+
*  40
*
*** ALCBK - Access-List Control Block
 
 
  ALCBK Cross Reference Top of page
 
 
Symbol         Dspl Value
-------------- ---- -----
ALCAL          0004
ALCALD         0000
ALCALSIZ       0030
ALCCSDWD       0038
ALCDEFRQ       0038
ALCFREE        003C
ALCLEN         003C 00000040
ALCLOCK        0018
ALCMAXSZ       0034
ALCOWNER       0008
ALCSIZE        003C 00000008
ALCSPIBK       0010
 
This information is based on z/VM 7.3.0 Last updated on 22 Jun 2022 at 15:47:06 EDT.
Copyright IBM Corporation, 1990, 2022