SNA Buffer Pool Control Block

The SNA buffer pool control block (SNBP) is built as the result of a SNABUF initialization statement. For each buffer pool, storage is obtained at BDT initialization for an SNBP, extent entries, and buffers for the primary extent. Secondary extents are acquired dynamically. The SNBP contains information describing that buffer pool, including a pointer to each extent, the buffer size, the number of buffers in each extent, the maximum number of secondary extents, and the number of available buffers.

Function:

Provides information describing a buffer pool

Macro ID:

BDTDSNB

DSECT name:

SNBP

Created by:

INR2 via BDTXGTMN

Size:

Hex 60 bytes

Accessed by:

INR1, INR2, IQCP, SCBUF, SCMGR, SCOCT

Location:

BDT address space

OFFSETS TYPE LENGTH NAME DESCRIPTION

      SNA BUFFER POOL

      MAPS THE SNA BUFFER POOL AND SNA INITIALIZATION
      CONTROL BLOCKS
      SNA BUFFER POOL CONTROL BLOCK

0     (0)    CHARACTER   4         SNBPID       CONTROL BLOCK ID
4     (4)    ADDRESS     4         SNBPNEXT     NEXT BUF POOL CONTROL BLOCK
8     (8)    ADDRESS     4         SNBPSIZE     BUFFER SIZE
12    (C)    ADDRESS     4         SNBPPXSZ     PRIMARY EXTENT SIZE
16    (10)   ADDRESS     4         SNPBSXSZ     SECONDARY EXTENT SIZE
20    (14)   ADDRESS     4         SNBPSXNO     NUMBER OF SECONDARY EXTENTS
24    (18)   ADDRESS     2         SNBPATF      ANTI THRASHING FACTOR (%)
26    (1A)   BITSTRING   1         SNBPFLG1     FLAGS
            1...  ....             SNBPADEL        "BIT0" AUTO DELETE
                                                   SECONDARY EXTNS

27    (1B)   BITSTRING   1         SNBPRSD1     RESERVED FOR DEVELOPMENT

      BUFFER POOL STATISTICS

28    (1C)   ADDRESS     4         SNBPTOTL     CURRENT SIZE OF BUFFER POOL
32    (20)   ADDRESS     4         SNBPINUS     CURRENT NUM OF BUF IN USE
36    (24)   ADDRESS     4         SNBPSEXT     CUR NUM OF SECONDARY EXTENTS
40    (28)   ADDRESS     4         SNBPDPLT     NUM OF TIMES BUF PL DEPLETED
44    (2C)   ADDRESS     4         SNBPMXSZ     MAXIMUM SIZE OF BUFFER POOL
48    (30)   ADDRESS     4         SNBPMXUS     MAX NUMBER OF BUFFER IN USE
52    (34)   ADDRESS     4         SNBPMXSE     MAX NUM OF SECONDARY EXTENTS
56    (38)   BITSTRING   1         SNBPSUBI     SUBPOOL FOR SNA BUFFER POOLS
57    (39)   BITSTRING   1         SNBPRSD2     RESERVED FOR DEVELOPMENT
60    (3C)   ADDRESS     4         SNBPRSD3     RESERVED FOR DEVELOPMENT
            ....  ....             SNBPFIXD        LENGTH = L'SNBPFIXD

      EXTENT ENTRY

64    (40)   ADDRESS     4         SNBPXPTR     POINTER TO THE EXTENT
68    (44)   ADDRESS     4         SNBPXCNT     NUM OF AVAILABLE BUF IN THE
                                                   EXTENT
72    (48)   FIXED       4         SNBPXNXT     ALIGN TO START OF NEXT ENT
            .1..  ....             SNBPXENT        LENGTH = L'SNBPXENT

      SNA BUFFER POOL EXTENT

0     (0)    ADDRESS     4         SNBPXSIZ     AMOUNT OF STORAGE OBTAINED
                                                   FOR THIS EXTENT
4     (4)    ADDRESS     4                      RESERVED
8     (8)    ADDRESS     4         SNBPXAVL     FIRST AVAILABLE BUFFER
12    (C)    ADDRESS     4         SNBPXQUC     QUEUE UPDATE COUNT
            ....  1...             SNBPXHDR        FIRST AVAILABLE BUFFER

16    (10)   ADDRESS     4         SNBPXFST     FIRST BUFFER IN THIS EXTENT
20    (14)   ADDRESS     4         SNBPXLST     LAST BUFFER IN THIS EXTENT
24    (18)   FIXED       4         SNBPXBUF     FIRST BUFFER IN THIS EXTENT

            ....  ....             SNBPXPFX        LENGTH = L'SNBPXPFX