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 DSECT
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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 - 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

 
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