strace和10046 研究一致读

SQL> create table t as select object_id,owner from dba_objects where rownum < 1000;  
  
表已创建。  
  
SQL> alter table t add constraint t_id_pk primary key(object_id);

SQL> update t set owner='AA' where object_id=500;

已更新 1 行。



SQL>  select xidusn,xidslot,xidsqn,ubablk,ubafil,ubarec,to_char(START_SCN,'9999999999999') from v$transaction;

    XIDUSN    XIDSLOT	  XIDSQN     UBABLK	UBAFIL	   UBAREC TO_CHAR(START_
---------- ---------- ---------- ---------- ---------- ---------- --------------
	 6	    6	    1942       3683	     3	       13	 4119141

SQL>  select name from v$rollname where usn=6;

NAME
------------------------------
_SYSSMU6_2897970769$



SESSION2:

SQL> select spid from v$process where addr=(select paddr from v$session where sid=(select sid from v$mystat where rownum < 2));

SPID
------------------------
8463

SQL>  alter system flush BUFFER_CACHE;

系统已更改。

SQL> ALTER SESSION SET EVENTS '10046 trace name context forever, level 12';

会话已更改。

SQL>  select * from test.t where  object_id=500;

 OBJECT_ID OWNER
---------- ------------------------------
       500 SYS

SQL>  ALTER SESSION SET EVENTS '10046 trace name context off';

会话已更改。


=====================
PARSING IN CURSOR #3 len=42 dep=0 uid=91 oct=3 lid=91 tim=1406434400557799 hv=3232312308 ad='24f4f408' sqlid='gqqq2p30akazn'
 select * from test.t where  object_id=500
END OF STMT
PARSE #3:c=2000,e=2579,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=51703167,tim=1406434400537084
EXEC #3:c=0,e=117,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=51703167,tim=1406434400558001
WAIT #3: nam='SQL*Net message to client' ela= 6 driver id=1650815232 #bytes=1 p3=0 obj#=383 tim=1406434400558190
WAIT #3: nam='Disk file operations I/O' ela= 82 FileOperation=2 fileno=10 filetype=2 obj#=76193 tim=1406434400558384
WAIT #3: nam='db file sequential read' ela= 15 file#=10 block#=14593 blocks=1 obj#=76193 tim=1406434400558446
WAIT #3: nam='db file sequential read' ela= 9 file#=10 block#=14594 blocks=1 obj#=76193 tim=1406434400558527
WAIT #3: nam='db file sequential read' ela= 7 file#=10 block#=257 blocks=1 obj#=76192 tim=1406434400558557
WAIT #3: nam='db file sequential read' ela= 62 file#=3 block#=208 blocks=1 obj#=0 tim=1406434400558686
WAIT #3: nam='db file sequential read' ela= 8 file#=3 block#=3683 blocks=1 obj#=0 tim=1406434400558743
FETCH #3:c=0,e=542,p=5,cr=5,cu=0,mis=0,r=1,dep=0,og=1,plh=51703167,tim=1406434400558783
STAT #3 id=1 cnt=1 pid=0 pos=1 obj=76192 op='TABLE ACCESS BY INDEX ROWID T (cr=5 pr=5 pw=0 time=0 us cost=1 size=30 card=1)'
STAT #3 id=2 cnt=1 pid=1 pos=1 obj=76193 op='INDEX UNIQUE SCAN T_ID_PK (cr=2 pr=2 pw=0 time=0 us cost=1 size=0 card=1)'
WAIT #3: nam='SQL*Net message from client' ela= 217 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1406434400577021
FETCH #3:c=0,e=1,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=0,plh=51703167,tim=1406434400577053
WAIT #3: nam='SQL*Net message to client' ela= 2 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1406434400577069

*** 2014-07-27 12:13:26.343
WAIT #3: nam='SQL*Net message from client' ela= 5766213 driver id=1650815232 #bytes=1 p3=0 obj#=0 tim=1406434406343299
CLOSE #3:c=0,e=17,dep=0,type=0,tim=1406434406343380
=====================
PARSING IN CURSOR #4 len=56 dep=0 uid=91 oct=42 lid=91 tim=1406434406343642 hv=3621752648 ad='0' sqlid='5p1y8sgbxz3u8'
 ALTER SESSION SET EVENTS '10046 trace name context off'
END OF STMT
PARSE #4:c=0,e=234,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=0,plh=0,tim=1406434406343641
EXEC #4:c=0,e=243,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=0,plh=0,tim=1406434406343915

WAIT #3: nam='db file sequential read' ela= 15 file#=10 block#=14593 blocks=1 obj#=76193 tim=1406434400558446
WAIT #3: nam='db file sequential read' ela= 9 file#=10 block#=14594 blocks=1 obj#=76193 tim=1406434400558527
WAIT #3: nam='db file sequential read' ela= 7 file#=10 block#=257 blocks=1 obj#=76192 tim=1406434400558557
WAIT #3: nam='db file sequential read' ela= 62 file#=3 block#=208 blocks=1 obj#=0 tim=1406434400558686
WAIT #3: nam='db file sequential read' ela= 8 file#=3 block#=3683 blocks=1 obj#=0 tim=1406434400558743
其中:

SQL>  select object_name from dba_objects  where object_id=76193;

OBJECT_NAME
--------------------------------------------------------------------------------
T_ID_PK

SQL>  select object_name from dba_objects  where object_id=76192;

OBJECT_NAME
--------------------------------------------------------------------------------
T

select segment_name,header_file,header_block from dba_segments where segment_name='_SYSSMU6_2897970769$'SQL> 
  2  ;

SEGMENT_NAME	     HEADER_FILE HEADER_BLOCK
-------------------- ----------- ------------
_SYSSMU6_2897970769$	       3	  208

WAIT #3: nam='db file sequential read' ela= 62 file#=3 block#=208 blocks=1 obj#=0 tim=1406434400558686

_SYSSMU6_2897970769$的块头

WAIT #3: nam='db file sequential read' ela= 8 file#=3 block#=3683 blocks=1 obj#=0 tim=1406434400558743


SQL> select owner, segment_name, segment_type      
  from dba_extents      
 where file_id = 3    
   and 3683 between block_id      
   and block_id + blocks - 1   2    3    4    5  ;

OWNER			       SEGMENT_NAME	    SEGMENT_TYPE
------------------------------ -------------------- ------------------
SYS			       _SYSSMU6_2897970769$ TYPE2 UNDO

顺序是读索引块14593和14594 读表块257 读UNDO HEADER 208 读UNDO块3683



sreace 跟踪:

[oracle@june2 ~]$ cat 8463.txt 
8463  read(13, "352621i:376377377377133^;a200"..., 8208) = 234
8463  gettimeofday({1406435222, 138141}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  gettimeofday({1406435222, 138423}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  gettimeofday({1406435222, 138551}, NULL) = 0
8463  gettimeofday({1406435222, 138567}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  gettimeofday({1406435222, 138726}, NULL) = 0
8463  gettimeofday({1406435222, 138829}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  gettimeofday({1406435222, 138917}, NULL) = 0
8463  gettimeofday({1406435222, 138932}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  gettimeofday({1406435222, 138989}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  gettimeofday({1406435222, 139078}, NULL) = 0
8463  gettimeofday({1406435222, 139099}, NULL) = 0
8463  gettimeofday({1406435222, 139117}, NULL) = 0
8463  gettimeofday({1406435222, 139135}, NULL) = 0
8463  gettimeofday({1406435222, 139168}, NULL) = 0
8463  gettimeofday({1406435222, 139184}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  gettimeofday({1406435222, 139302}, NULL) = 0
8463  gettimeofday({1406435222, 139317}, NULL) = 0
8463  pread64(18, "62420192002L332>14272352241)1K332>"..., 8192, 119545856) = 8192
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  pread64(18, "62420292002L332>24q'2241)1K332>"..., 8192, 119554048) = 8192
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  gettimeofday({1406435222, 139418}, NULL) = 0
8463  pread64(18, "6242112002252334>14/31240)1252334>"..., 8192, 2105344) = 8192
8463  gettimeofday({1406435222, 139803}, NULL) = 0
8463  gettimeofday({1406435222, 139822}, NULL) = 0
8463  gettimeofday({1406435222, 139855}, NULL) = 0
8463  gettimeofday({1406435222, 139871}, NULL) = 0
8463  pread64(12, "&242320300e332>14330345"..., 8192, 1703936) = 8192
8463  gettimeofday({1406435222, 139923}, NULL) = 0
8463  gettimeofday({1406435222, 139940}, NULL) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  gettimeofday({1406435222, 140017}, NULL) = 0
8463  gettimeofday({1406435222, 140032}, NULL) = 0
8463  pread64(12, "2242c16300e332>1432246622673353

"..., 8192, 30171136) = 8192
8463  gettimeofday({1406435222, 140198}, NULL) = 0
8463  gettimeofday({1406435222, 140215}, NULL) = 0
8463  gettimeofday({1406435222, 140292}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  gettimeofday({1406435222, 140343}, NULL) = 0
8463  gettimeofday({1406435222, 140362}, NULL) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  getrusage(RUSAGE_SELF, {ru_utime={0, 249962}, ru_stime={0, 65989}, ...}) = 0
8463  times({tms_utime=24, tms_stime=6, tms_cutime=0, tms_cstime=0}) = 448603871
8463  gettimeofday({1406435222, 140444}, NULL) = 0
8463  write(16, "122562027336Orv342370a21710321266270R35426517x"..., 405) = 405
8463  read(13,  <unfinished ...>

打开的文件描述符为:
[oracle@june2 ~]$ cat 8463.txt | grep 8192
8463  pread64(18, "62420192002L332>14272352241)1K332>"..., 8192, 119545856) = 8192
8463  pread64(18, "62420292002L332>24q'2241)1K332>"..., 8192, 119554048) = 8192
8463  pread64(18, "6242112002252334>14/31240)1252334>"..., 8192, 2105344) = 8192
8463  pread64(12, "&242320300e332>14330345"..., 8192, 1703936) = 8192
8463  pread64(12, "2242c16300e332>1432246622673353

"..., 8192, 30171136) = 8192

lrwx------ 1 oracle dba 64 07-27 12:25 18 -> /oradata/june/test2.dbf

访问第一个数据块号为:
SQL>  select 119545856/8192 from dual;

119545856/8192
--------------
	 14593


访问第二个数据块号为:
SQL> select 119554048/8192 from dual;

119554048/8192
--------------
	 14594

访问的第三个数据块号为；
SQL>  select 2105344/8192 from dual;

2105344/8192
------------
	 257

访问的第四个块号为:
SQL> select 1703936/8192 from dual;

1703936/8192
------------
	 208

访问的第五个块号为:
SQL> select 30171136/8192 from dual;

30171136/8192
-------------
	 3683


strace 和10046的结果完全一致