MBBK Back to Index page
 
Prolog 
Control Block Contents 
   MBBK 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.


  MBBK Prolog Top of page
 
 NAME       : HCPMBBK
 DESCRIPTION: Managed Buffers Set Block
 DSECT      : MBBK
 FUNCTION   : A Managed Buffer Set Block will contain information
              about the buffers managed by module HCPMBS.
 LOCATED BY : MBBKs are chained in a circular double linked list.
              The start of the linked list is anchored at
              RSAFMBBK.  The forward pointer of the last block
              points to the block at RSAFMBBK.  The backward
              pointer of the block at RSAFMBBK points to the last
              block.  If there are no blocks in the list, RSAFMBBK
              contains 0.
 CREATED BY : A Managed Buffer Block is allocated by
              HCPMBSIN in HCPMBS. This occurs during the
              Managed Buffer Set initialization.
 DELETED BY : A Managed Buffer Block is deleted by HCPMBSCL
              in HCPMBS. This occurs when the Managed
              Buffer Set is being closed.
              It can also be deleted by HCPMBS1R/RM and
              HCPMBSCB when the Managed Buffer Set Block
              was closed before the call to these entry
              points.
 REFERENCES : See HCPMBS for information about the usage of
              this block.
 SERIALIZED : MBBNEXT and MBBPREV are serialized by
              RSAMBSLK in HCPMBS. The rest of the fields
              are serialized by MBBLK. Both of these
              locks are acquired by the TS instruction.
 RELOCATION CONSIDERATIONS : None
 NOTES      : None
 
 
  MBBK Control Block Content Top of page
 

 MBBK DSECT Top of page
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure MBBK Managed Buffers Set Block 0000 0 Address 4 MBBNEXT Next MBBK 0004 4 Address 4 MBBPREV Previous MBBK 0008 8 Bitstring 1 MBBLK Managed Buffer Set Block Lock 0009 9 Bitstring 1 MBBSTATE Managed Buffer Set State 1... .... MBBCLOSE X'80' MBBCLOSE Indicates that this Managed Buffer Set is closed. 000A 10 Bitstring 1 MBBCALLR MBBK GB/GM caller codes .... ...1 MBBGB 1 MBBGB Caller of HCPMBSGB .... ..1. MBBGM 2 MBBGM Caller of HCPMBSGM 000B 11 Bitstring 1 * Reserved for IBM use 000C 12 Signed 4 MBBMAX Maximum number of buffers that can be allocated by this managed buffer set. 0010 16 Signed 4 MBBRQMAX Requested max, passed in to HCPMBSIN 0014 20 Signed 4 MBBCOUT Count of Buffers currently allocated 0018 24 Signed 4 MBBPCOUT Count of Pending Out buffers... requested, not yet allocated A waiting queue will be maintained for processes that requested a buffer while all the buffers were out and the number of allocated buffers has reached the maximum permitted. Notes : The waiting queue is only used when MBBCALLR=MBBGB. 001C 28 Address 4 MBBWQHD Requesters Waiting Queue Head 0020 32 Address 4 MBBWQTL Requesters Waiting Queue Tail 0024 36 Signed 4 * (4) Reserved for future use The following counters are useful for debugging. 0034 52 Signed 4 MBBMXOUT Maximum achieved value of out buffers 0038 56 Signed 4 MBBNBPMX No-buffer-provided max count Keeps track of how many times MBS could not provide a buffer (MBSGB or MBSGM caller) due to max reached 003C 60 Signed 4 MBBDEFER Cumulative count of requests (MBSGB or MBSGM requests) that were told to defer Notes : MBBTOTAL = MBBRBREQ + MBBCBREQ + MBBCOUT 0040 64 Signed 4 MBBTOTAL Total number of buffers allocated 0044 68 Signed 4 MBBRBREQ Cumulative count of buffers returned 0048 72 Signed 4 MBBCBREQ Cumulative count of consumed buffers 0000000A MBBSIZE (*-MBBK+7)/8 size in double words 00000050 MBBBSIZE MBBSIZE*8 size in bytes
 
 
  MBBK Storage Layout Top of page
 
          
*** MBBK - Managed Buffers Set Block
*
*     +---------------------------+---------------------------+
*   0 |         MBBNEXT           |         MBBPREV           |
*     +------+------+------+------+---------------------------+
*   8 |MBBLK |:STATE|:CALLR|//////|          MBBMAX           |
*     +------+------+------+------+---------------------------+
*  10 |         MBBRQMAX          |         MBBCOUT           |
*     +---------------------------+---------------------------+
*  18 |         MBBPCOUT          |         MBBWQHD           |
*     +---------------------------+---------------------------+
*  20 |         MBBWQTL           |///////////////////////////|
*     +---------------------------+///////////////////////////|
*     |///////////////////////////////////////////////////////|
*     |///////////////////////////+---------------------------+
*  30 |///////////////////////////|         MBBMXOUT          |
*     +---------------------------+---------------------------+
*  38 |         MBBNBPMX          |         MBBDEFER          |
*     +---------------------------+---------------------------+
*  40 |         MBBTOTAL          |         MBBRBREQ          |
*     +---------------------------+---------------------------+
*  48 |         MBBCBREQ          | 4C
*     +---------------------------+
*
*** MBBK - Managed Buffers Set Block
 
 
  MBBK Cross Reference Top of page
 
 
Symbol         Dspl Value
-------------- ---- -----
MBBBSIZE       0048 00000050
MBBCALLR       000A
MBBCBREQ       0048
MBBCLOSE       0009 80
MBBCOUT        0014
MBBDEFER       003C
MBBGB          000A 01
MBBGM          000A 02
MBBLK          0008
MBBMAX         000C
MBBMXOUT       0034
MBBNBPMX       0038
MBBNEXT        0000
MBBPCOUT       0018
MBBPREV        0004
MBBRBREQ       0044
MBBRQMAX       0010
MBBSIZE        0048 0000000A
MBBSTATE       0009
MBBTOTAL       0040
MBBWQHD        001C
MBBWQTL        0020
 
This information is based on z/VM 7.3.0 Last updated on 22 Jun 2022 at 15:52:29 EDT.
Copyright IBM Corporation, 1990, 2022