[20150122]buffer busy waits特例.txt

lfreeali 2015-01-23

Cache 测试 test DBA metadata dump

[20150122]buffer busy waits特例.txt

--oracle 里有句名言:读不阻塞写,写阻塞读.
--如果读读模式,是否会出现buffer busy waits呢?通过例子来说明:

1.建立测试环境:

SCOTT@test> @ver1

PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.3.0     Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production

SCOTT@test> create table t as select rownum id,'test' data from dual connect by levelTable created.

SCOTT@test> @stats t
exec sys.dbms_stats.gather_table_stats ( OwnName => user,TabName => 't',Estimate_Percent => NULL,Method_Opt => 'FOR ALL COLUMNS SIZE 1 ',Cascade => True ,No_Invalidate => false)
PL/SQL procedure successfully completed.

SCOTT@test> select rowid,t.* from t where id=42;
ROWID                      ID DATA
------------------ ---------- ----
AABIwbAAEAAAAfjAAp         42 test

SCOTT@test> @lookup_rowid AABIwbAAEAAAAfjAAp
    OBJECT       FILE      BLOCK        ROW DBA                  TEXT
---------- ---------- ---------- ---------- -------------------- ----------------------------------------
    298011          4       2019         41 4,2019               alter system dump datafile 4 block 2019
 
--建立测试脚本:
$ cat f1.sql
declare
m_id number;
m_data varchar2(200);
begin
        for i in 1 .. 1e9 loop
                select data into m_data from t where id = 42;
end loop;
end ;
/

$ cat f.sh
#! /bin/bash
sqlplus -s scott/btbtms @$1 &
sqlplus -s scott/btbtms @$1 &
sqlplus -s scott/btbtms @$1 &
sqlplus -s scott/btbtms @$1 &

2.开始测试:

$ source f.sh f1.sql

SCOTT@test> select p1raw,p2raw,sid,serial#,seq#,event,state,wait_time_micro,seconds_in_wait from v$session where wait_class'Idle' order by event ;
P1RAW            P2RAW                   SID    SERIAL#       SEQ# EVENT                                    STATE               WAIT_TIME_MICRO SECONDS_IN_WAIT
---------------- ---------------- ---------- ---------- ---------- ---------------------------------------- ------------------- --------------- ---------------
0000000062657100 0000000000000001          6         15       1415 SQL*Net message to client                WAITED SHORT TIME                 2               0
00000000664C4F47 0000000000000001        203         75         54 cursor: pin S                            WAITED SHORT TIME                 7               0
00000000BC9103C8 000000000000009B        596         43         47 latch: cache buffers chains              WAITED SHORT TIME               437               1
00000000BC9103C8 000000000000009B        395         25         43 latch: cache buffers chains              WAITED SHORT TIME               463               1
00000000BC9103C8 000000000000009B         12         43         55 latch: cache buffers chains              WAITED SHORT TIME               494               1

--再增加4个会话:
$ source f.sh f1.sql

SCOTT@test> select p1raw,p2raw,sid,serial#,seq#,event,state,wait_time_micro,seconds_in_wait from v$session where wait_class'Idle' order by event ;
P1RAW            P2RAW                   SID    SERIAL#       SEQ# EVENT                                    STATE               WAIT_TIME_MICRO SECONDS_IN_WAIT
---------------- ---------------- ---------- ---------- ---------- ---------------------------------------- ------------------- --------------- ---------------
0000000062657100 0000000000000001          6         15       1491 SQL*Net message to client                WAITED SHORT TIME                 3               0
00000000664C4F47 0000018F00000007         12         43        182 cursor: pin S                            WAITED KNOWN TIME             10906               1
00000000664C4F47 0000018F00000007        203         75        187 cursor: pin S                            WAITED KNOWN TIME             10854               1
00000000664C4F47 0000018F00000007        595         15        120 cursor: pin S                            WAITED KNOWN TIME            221355               1
00000000664C4F47 0000018F00000007        596         43        195 cursor: pin S                            WAITED KNOWN TIME             23502               1
00000000664C4F47 0000018F00000007        201         47        118 cursor: pin S                            WAITED KNOWN TIME             11327               1
00000000BC8D0380 000000000000009B        399         27        117 latch: cache buffers chains              WAITED SHORT TIME                64               0
00000000BC8D0380 000000000000009B        395         25        188 latch: cache buffers chains              WAITED SHORT TIME               458               0
00000000BC8D0380 000000000000009B         14         53        121 latch: cache buffers chains              WAITING                        5281               0

9 rows selected.

--再增加4个会话:
$ source f.sh f1.sql

-- 依旧没有出现buffer busy waits.


3.测试2,建立表大一些.

SCOTT@test> create table t as select rownum id,'test' data from dual connect by levelTable created.

SCOTT@test> ALTER TABLE t MINIMIZE RECORDS_PER_BLOCK ;
Table altered.
--这样每块仅仅2条记录,可以很快建立"大表".

SCOTT@test> delete from  t ;
2 rows deleted.

SCOTT@test> commit ;
Commit complete.

SCOTT@test> insert into t  select rownum id,'test' data from dual connect by level10000 rows created.

SCOTT@test> commit ;
Commit complete.

SCOTT@test> @stats t
exec sys.dbms_stats.gather_table_stats ( OwnName => user,TabName => 't',Estimate_Percent => NULL,Method_Opt => 'FOR ALL COLUMNS SIZE 1 ',Cascade => True ,No_Invalidate => false)
PL/SQL procedure successfully completed.


SCOTT@test> select header_file,header_block,bytes,blocks from dba_segments where owner=user and segment_name='T';
HEADER_FILE HEADER_BLOCK      BYTES     BLOCKS
----------- ------------ ---------- ----------
          4         1802   41943040       5120

SCOTT@test> select p1raw,p2raw,sid,serial#,seq#,event,state,wait_time_micro,seconds_in_wait from v$session where wait_class'Idle' order by event ;
P1RAW            P2RAW                   SID    SERIAL#       SEQ# EVENT                                    STATE               WAIT_TIME_MICRO SECONDS_IN_WAIT
---------------- ---------------- ---------- ---------- ---------- ---------------------------------------- ------------------- --------------- ---------------
0000000062657100 0000000000000001        406         37       5399 SQL*Net message to client                WAITED SHORT TIME                 4               0
0000000000000004 000000000000070A        206         55         55 buffer busy waits                        WAITED SHORT TIME                18               0
0000000000000004 000000000000070A        207         43         93 buffer busy waits                        WAITED SHORT TIME                15               1
00000000BCA208E0 000000000000009B        400         69         73 latch: cache buffers chains              WAITED SHORT TIME                54               0
00000000BCA208E0 000000000000009B        205         21        106 latch: cache buffers chains              WAITED SHORT TIME                45               1

--可以发现很快出现buffer busy waits.

SCOTT@test> select * from V$EVENT_NAME where name='buffer busy waits';
    EVENT#   EVENT_ID NAME                 PARAMETER1           PARAMETER2           PARAMETER3           WAIT_CLASS_ID WAIT_CLASS# WAIT_CLASS
---------- ---------- -------------------- -------------------- -------------------- -------------------- ------------- ----------- --------------------
        94 2161531084 buffer busy waits    file#                block#               class#                  3875070507           4 Concurrency

--可以发现参数P1表示file#,P2表示block#. 000000000000070A(16进制)
SCOTT@test> @16to10 70a
16 to 10 DEC
------------
        1802

--正好是段头.也就是即使在读读模式,对于段头,buffer herder的buffer bin要设置为排他模式,这样才会出现buffer busy waits.
--因为段头保存extent map,全表扫描要多次读取.

  Auxillary Map
  --------------------------------------------------------
   Extent 0     :  L1 dba:  0x01000708 Data dba:  0x0100070b
   Extent 1     :  L1 dba:  0x01000708 Data dba:  0x01000710
   Extent 2     :  L1 dba:  0x01000718 Data dba:  0x01000719
   Extent 3     :  L1 dba:  0x01000718 Data dba:  0x01000720
   Extent 4     :  L1 dba:  0x01000728 Data dba:  0x01000729
   Extent 5     :  L1 dba:  0x01000728 Data dba:  0x01000730
   Extent 6     :  L1 dba:  0x01000738 Data dba:  0x01000739
   Extent 7     :  L1 dba:  0x01000738 Data dba:  0x01000740
   Extent 8     :  L1 dba:  0x01000748 Data dba:  0x01000749
   Extent 9     :  L1 dba:  0x01000748 Data dba:  0x01000750
   Extent 10    :  L1 dba:  0x01000758 Data dba:  0x01000759
   Extent 11    :  L1 dba:  0x01000758 Data dba:  0x01000768
   Extent 12    :  L1 dba:  0x01000770 Data dba:  0x01000771
   Extent 13    :  L1 dba:  0x01000770 Data dba:  0x010007c8
   Extent 14    :  L1 dba:  0x010007d0 Data dba:  0x010007d1
   Extent 15    :  L1 dba:  0x010007d0 Data dba:  0x010007d8
   Extent 16    :  L1 dba:  0x01000b00 Data dba:  0x01000b02
   Extent 17    :  L1 dba:  0x01000b80 Data dba:  0x01000b82
   Extent 18    :  L1 dba:  0x01000c80 Data dba:  0x01000c82
   Extent 19    :  L1 dba:  0x01000e00 Data dba:  0x01000e02
   Extent 20    :  L1 dba:  0x01000f00 Data dba:  0x01000f02
   Extent 21    :  L1 dba:  0x01001080 Data dba:  0x01001082
   Extent 22    :  L1 dba:  0x01001180 Data dba:  0x01001182
   Extent 23    :  L1 dba:  0x01001300 Data dba:  0x01001302
   Extent 24    :  L1 dba:  0x01001480 Data dba:  0x01001482
   Extent 25    :  L1 dba:  0x01001600 Data dba:  0x01001602
   Extent 26    :  L1 dba:  0x01001700 Data dba:  0x01001702
   Extent 27    :  L1 dba:  0x01001800 Data dba:  0x01001802
   Extent 28    :  L1 dba:  0x01001980 Data dba:  0x01001982
   Extent 29    :  L1 dba:  0x01001a80 Data dba:  0x01001a82
   Extent 30    :  L1 dba:  0x01001c00 Data dba:  0x01001c02
   Extent 31    :  L1 dba:  0x01001d00 Data dba:  0x01001d02
   Extent 32    :  L1 dba:  0x01001d80 Data dba:  0x01001d82
   Extent 33    :  L1 dba:  0x01001e00 Data dba:  0x01001e02
   Extent 34    :  L1 dba:  0x01001e80 Data dba:  0x01001e82
   Extent 35    :  L1 dba:  0x01001f00 Data dba:  0x01001f02
   Extent 36    :  L1 dba:  0x01001f80 Data dba:  0x01001f82
   Extent 37    :  L1 dba:  0x01002000 Data dba:  0x01002002
   Extent 38    :  L1 dba:  0x01002080 Data dba:  0x01002082
   Extent 39    :  L1 dba:  0x01002100 Data dba:  0x01002102
   Extent 40    :  L1 dba:  0x01002180 Data dba:  0x01002182
   Extent 41    :  L1 dba:  0x01002200 Data dba:  0x01002202
   Extent 42    :  L1 dba:  0x01002280 Data dba:  0x01002282
   Extent 43    :  L1 dba:  0x01002300 Data dba:  0x01002302
   Extent 44    :  L1 dba:  0x01002380 Data dba:  0x01002382
   Extent 45    :  L1 dba:  0x01002400 Data dba:  0x01002402
   Extent 46    :  L1 dba:  0x01002480 Data dba:  0x01002482
   Extent 47    :  L1 dba:  0x01002500 Data dba:  0x01002502
   Extent 48    :  L1 dba:  0x01002580 Data dba:  0x01002582
   Extent 49    :  L1 dba:  0x01002600 Data dba:  0x01002602
   Extent 50    :  L1 dba:  0x01002680 Data dba:  0x01002682
   Extent 51    :  L1 dba:  0x01002700 Data dba:  0x01002702
   Extent 52    :  L1 dba:  0x01002780 Data dba:  0x01002782
   Extent 53    :  L1 dba:  0x01002800 Data dba:  0x01002802
   Extent 54    :  L1 dba:  0x01002880 Data dba:  0x01002882
  --------------------------------------------------------

   Second Level Bitmap block DBAs
   --------------------------------------------------------
   DBA 1:   0x01000709

End dump data blocks tsn: 4 file#: 4 minblk 1802 maxblk 1802

--为什么测试1没有出现呢?与表的大小有关吗?继续测试.

4.为了测试方便,加入如下脚本:

$ cat b1.sql
drop table t purge ;
create table t (id number,data varchar2(20));
insert into t  select rownum id,'name' data from dual connect by levelALTER TABLE t MINIMIZE RECORDS_PER_BLOCK ;
delete from t;
commit ;
insert into t  select rownum id,'name' data from dual connect by level@stats t
select header_file,header_block,bytes,blocks from dba_segments where owner=user and segment_name='T';

-- 我的测试插入257条记录,就会出现buffer busy waits等待事件.
-- 注意我使用的表空间是系统管理表空间,8k.

SCOTT@test> column PARTITION_NAME noprint
SCOTT@test> select * from dba_extents where owner=user and segment_name='T';
OWNER  SEGMENT_NAME  SEGMENT_TYPE  TABLESPACE_NAME   EXTENT_ID    FILE_ID   BLOCK_ID      BYTES     BLOCKS RELATIVE_FNO
------ ------------- ------------- ---------------- ---------- ---------- ---------- ---------- ---------- ------------
SCOTT  T             TABLE         USERS                     0          4       1800      65536          8            4
SCOTT  T             TABLE         USERS                     1          4       1808      65536          8            4
SCOTT  T             TABLE         USERS                     2          4       1816      65536          8            4
SCOTT  T             TABLE         USERS                     3          4       1824      65536          8            4
SCOTT  T             TABLE         USERS                     4          4       1832      65536          8            4
SCOTT  T             TABLE         USERS                     5          4       1840      65536          8            4
SCOTT  T             TABLE         USERS                     6          4       1848      65536          8            4
SCOTT  T             TABLE         USERS                     7          4       1856      65536          8            4
SCOTT  T             TABLE         USERS                     8          4       1864      65536          8            4
SCOTT  T             TABLE         USERS                     9          4       1872      65536          8            4
SCOTT  T             TABLE         USERS                    10          4       1880      65536          8            4
SCOTT  T             TABLE         USERS                    11          4       1896      65536          8            4
SCOTT  T             TABLE         USERS                    12          4       1904      65536          8            4
SCOTT  T             TABLE         USERS                    13          4       1992      65536          8            4
SCOTT  T             TABLE         USERS                    14          4       2000      65536          8            4
SCOTT  T             TABLE         USERS                    15          4       2008      65536          8            4
SCOTT  T             TABLE         USERS                    16          4       2816    1048576        128            4
17 rows selected.

-- 每块2条记录,前面16个EXTENT_ID,占用8块. 这样16*8*2 = 256条. 也就是开始使用extend大小1M(128块的)时候,在全表扫描时出现时,会出现
-- buffer busy waits.
-- 实际上块里面包含段头,1级位图,2级位图,前面0-15extetnd,有8个1级位图,1个2级位图,1个段头(兼3级位图),插入256-10*2=236条以后都在
-- EXTENT_ID=16的区域.
-- 另外测试时要注意另外一个细节: 11G的direct path direct.

SCOTT@test> alter system checkpoint ;
System altered.

SCOTT@test> alter system dump datafile 4 block 1802;
System altered.

  Extent Control Header
  -----------------------------------------------------------------
  Extent Header:: spare1: 0      spare2: 0      #extents: 17     #blocks: 256
                  last map  0x00000000  #maps: 0      offset: 2716
      Highwater::  0x01000b80  ext#: 16     blk#: 128    ext size: 128
  #blocks in seg. hdr's freelists: 0
  #blocks below: 244
  mapblk  0x00000000  offset: 16
                   Unlocked
  --------------------------------------------------------
  Low HighWater Mark :
      Highwater::  0x010007e0  ext#: 15     blk#: 8      ext size: 8
  #blocks in seg. hdr's freelists: 0
  #blocks below: 118
  mapblk  0x00000000  offset: 15
  Level 1 BMB for High HWM block: 0x01000b01
  Level 1 BMB for Low HWM block: 0x010007d0
  --------------------------------------------------------
  Segment Type: 1 nl2: 1      blksz: 8192   fbsz: 0
  L2 Array start offset:  0x00001434
  First Level 3 BMB:  0x00000000
  L2 Hint for inserts:  0x01000709
  Last Level 1 BMB:  0x01000b01
  Last Level II BMB:  0x01000709
  Last Level III BMB:  0x00000000
     Map Header:: next  0x00000000  #extents: 17   obj#: 298135 flag: 0x10000000
  Inc # 0

  Extent Map
  -----------------------------------------------------------------
   0x01000708  length: 8
   0x01000710  length: 8
   0x01000718  length: 8
   0x01000720  length: 8
   0x01000728  length: 8
   0x01000730  length: 8
   0x01000738  length: 8
   0x01000740  length: 8
   0x01000748  length: 8
   0x01000750  length: 8
   0x01000758  length: 8
   0x01000768  length: 8
   0x01000770  length: 8
   0x010007c8  length: 8
   0x010007d0  length: 8
   0x010007d8  length: 8
   0x01000b00  length: 128

  Auxillary Map
  --------------------------------------------------------
   Extent 0     :  L1 dba:  0x01000708 Data dba:  0x0100070b
   Extent 1     :  L1 dba:  0x01000708 Data dba:  0x01000710
   Extent 2     :  L1 dba:  0x01000718 Data dba:  0x01000719
   Extent 3     :  L1 dba:  0x01000718 Data dba:  0x01000720
   Extent 4     :  L1 dba:  0x01000728 Data dba:  0x01000729
   Extent 5     :  L1 dba:  0x01000728 Data dba:  0x01000730
   Extent 6     :  L1 dba:  0x01000738 Data dba:  0x01000739
   Extent 7     :  L1 dba:  0x01000738 Data dba:  0x01000740
   Extent 8     :  L1 dba:  0x01000748 Data dba:  0x01000749
   Extent 9     :  L1 dba:  0x01000748 Data dba:  0x01000750
   Extent 10    :  L1 dba:  0x01000758 Data dba:  0x01000759
   Extent 11    :  L1 dba:  0x01000758 Data dba:  0x01000768
   Extent 12    :  L1 dba:  0x01000770 Data dba:  0x01000771
   Extent 13    :  L1 dba:  0x01000770 Data dba:  0x010007c8
   Extent 14    :  L1 dba:  0x010007d0 Data dba:  0x010007d1
   Extent 15    :  L1 dba:  0x010007d0 Data dba:  0x010007d8
   Extent 16    :  L1 dba:  0x01000b00 Data dba:  0x01000b02
  --------------------------------------------------------

   Second Level Bitmap block DBAs
   --------------------------------------------------------
   DBA 1:   0x01000709

End dump data blocks tsn: 4 file#: 4 minblk 1802 maxblk 1802


SCOTT@test> alter system dump datafile 4 block 1800;
System altered.


Dump of First Level Bitmap Block
--------------------------------
   nbits : 4 nranges: 2         parent dba:  0x01000709   poffset: 0
   unformatted: 0       total: 16        first useful block: 3
   owning instance : 1
   instance ownership changed at 01/23/2015 10:38:43
   Last successful Search 01/23/2015 10:38:43
   Freeness Status:  nf1 0      nf2 0      nf3 0      nf4 0

   Extent Map Block Offset: 4294967295
   First free datablock : 16
   Bitmap block lock opcode 0
   Locker xid:     :  0x0000.000.00000000
   Dealloc scn: -887287252.2
   Flag: 0x00000000 (-/-/-/-/-/-)
   Inc #: 0 Objd: 298135
  --------------------------------------------------------
  DBA Ranges :
  --------------------------------------------------------
   0x01000708  Length: 8      Offset: 0
   0x01000710  Length: 8      Offset: 8

   0:Metadata   1:Metadata   2:Metadata   3:FULL
   4:FULL   5:FULL   6:FULL   7:FULL
   8:FULL   9:FULL   10:FULL   11:FULL
   12:FULL   13:FULL   14:FULL   15:FULL
  --------------------------------------------------------
End dump data blocks tsn: 4 file#: 4 minblk 1800 maxblk 1800

- 3-15 extent都是full.

SCOTT@test> alter system dump datafile 4 block 2816;
System altered.

Dump of First Level Bitmap Block
--------------------------------
   nbits : 4 nranges: 1         parent dba:  0x01000709   poffset: 8
   unformatted: 0       total: 64        first useful block: 2
   owning instance : 1
   instance ownership changed at 01/23/2015 10:38:43
   Last successful Search 01/23/2015 10:38:43
   Freeness Status:  nf1 0      nf2 0      nf3 0      nf4 53

   Extent Map Block Offset: 4294967295
   First free datablock : 2
   Bitmap block lock opcode 0
   Locker xid:     :  0x0000.000.00000000
   Dealloc scn: -887287252.2
   Flag: 0x00000000 (-/-/-/-/-/-)
   Inc #: 0 Objd: 298135
  --------------------------------------------------------
  DBA Ranges :
  --------------------------------------------------------
   0x01000b00  Length: 64     Offset: 0

   0:Metadata   1:Metadata   2:75-100% free   3:75-100% free
   4:75-100% free   5:FULL   6:75-100% free   7:75-100% free
   8:75-100% free   9:FULL   10:75-100% free   11:75-100% free
   12:75-100% free   13:FULL   14:75-100% free   15:75-100% free
   16:75-100% free   17:75-100% free   18:75-100% free   19:75-100% free
   20:75-100% free   21:75-100% free   22:75-100% free   23:75-100% free
   24:75-100% free   25:75-100% free   26:75-100% free   27:75-100% free
   28:75-100% free   29:75-100% free   30:75-100% free   31:75-100% free
   32:75-100% free   33:75-100% free   34:75-100% free   35:75-100% free
   36:75-100% free   37:75-100% free   38:75-100% free   39:75-100% free
   40:FULL   41:75-100% free   42:75-100% free   43:75-100% free
   44:FULL   45:75-100% free   46:75-100% free   47:75-100% free
   48:FULL   49:75-100% free   50:75-100% free   51:75-100% free
   52:FULL   53:75-100% free   54:75-100% free   55:75-100% free
   56:FULL   57:75-100% free   58:75-100% free   59:75-100% free
   60:FULL   61:75-100% free   62:75-100% free   63:75-100% free
  --------------------------------------------------------
End dump data blocks tsn: 4 file#: 4 minblk 2816 maxblk 2816

--对比不同就是插入256条记录时.

Dump of First Level Bitmap Block
--------------------------------
   nbits : 4 nranges: 1         parent dba:  0x01000709   poffset: 8
   unformatted: 16      total: 64        first useful block: 2
   owning instance : 1
   instance ownership changed at 01/23/2015 11:07:43
   Last successful Search 01/23/2015 11:07:43
   Freeness Status:  nf1 0      nf2 0      nf3 0      nf4 38

   Extent Map Block Offset: 4294967295
   First free datablock : 2
   Bitmap block lock opcode 0
   Locker xid:     :  0x0000.000.00000000
   Dealloc scn: -887058979.2
   Flag: 0x00000000 (-/-/-/-/-/-)
   Inc #: 0 Objd: 298137
  --------------------------------------------------------
  DBA Ranges :
  --------------------------------------------------------
   0x01000b00  Length: 64     Offset: 0

   0:Metadata   1:Metadata   2:75-100% free   3:FULL
   4:75-100% free   5:75-100% free   6:75-100% free   7:FULL
   8:75-100% free   9:75-100% free   10:75-100% free   11:75-100% free
   12:75-100% free   13:75-100% free   14:75-100% free   15:75-100% free
   16:unformatted   17:unformatted   18:unformatted   19:unformatted
   20:unformatted   21:unformatted   22:unformatted   23:unformatted
   24:unformatted   25:unformatted   26:unformatted   27:unformatted
   28:unformatted   29:unformatted   30:unformatted   31:unformatted
   32:75-100% free   33:75-100% free   34:75-100% free   35:75-100% free
   36:75-100% free   37:75-100% free   38:75-100% free   39:75-100% free
   40:75-100% free   41:75-100% free   42:FULL   43:75-100% free
   44:75-100% free   45:75-100% free   46:FULL   47:75-100% free
   48:75-100% free   49:75-100% free   50:FULL   51:75-100% free
   52:75-100% free   53:75-100% free   54:FULL   55:75-100% free
   56:75-100% free   57:75-100% free   58:FULL   59:75-100% free
   60:75-100% free   61:75-100% free   62:FULL   63:75-100% free
  --------------------------------------------------------
End dump data blocks tsn: 4 file#: 4 minblk 2816 maxblk 2816

--存在16个没有格式化的块.而插入257条记录,包含的块全表格式化.这些分析超出我的能力,放弃.

-- 总之表大小达到一定程度,在读读模式下,也会出现buffer busy waits.而且是段头.

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