[20181116]18c DML 日誌優化.txt

1.環境:

xxxxxxxx> select banner_full from v$version;

BANNER_FULL

-----------------------------------------------------------------------------

Oracle Database 18c Enterprise Edition Release 18.0.0.0.0 - Production

Version 18.3.0.0.0

2.建立測試指令碼:

xxxxxxxx> create table t as select rownum id ,lpad('y',200,'y') v1,lpad('z',100,'z') v2 from dual connect by level<=100;

Table created.

xxxxxxxx> select dump('x',16),dump('y',16),dump('z',16) from dual ;

DUMP('X',16) DUMP('Y',16) DUMP('Z',16)

-------------------------------- -------------------------------- --------------------------------

Typ=96 Len=1: 78 Typ=96 Len=1: 79 Typ=96 Len=1: 7a

xxxxxxxx> @ viewsess redo%size

NAME STATISTIC# VALUE SID

---------------------------------- ---------- -------------- ----------

redo size 293 684 258

redo size for lost write detection 295 0 258

redo size for direct writes 296 0 258

redo write size count ( 4KB) 321 0 258

redo write size count ( 8KB) 322 0 258

redo write size count ( 16KB) 323 0 258

redo write size count ( 32KB) 324 0 258

redo write size count ( 64KB) 325 0 258

redo write size count ( 128KB) 326 0 258

redo write size count ( 256KB) 327 0 258

redo write size count ( 512KB) 328 0 258

redo write size count (1024KB) 329 0 258

redo write size count (inf) 330 0 258

IMU Redo allocation size 736 0 258

14 rows selected.

--//建立測試指令碼a.txt

column member new_value v_member

column member noprint

set numw 12

alter system switch logfile ;

--//alter system archive log current;

--//12c以上不允許在pluggable database執行這條命令.注這個庫沒有開啟歸檔,alter system archive log current;會報錯.

--//採用alter system switch logfile ;.

SELECT member FROM v$log a, v$logfile b WHERE a.group#(+) = b.group# and a.STATUS='CURRENT' and rownum=1;

column curr1 new_value v_curr1

select current_scn curr1 from v$database;

--//以下操作DML內容:

update t set v1=lpad('y',200,'y') ,v2=lpad('z',100,'z');

commit ;

exec dbms_session.sleep(3);

column curr2 new_value v_curr2

select current_scn curr2 from v$database;

prompt exec DBMS_LOGMNR.START_LOGMNR(STARTSCN => &&v_curr1 ,ENDSCN => &&v_curr2 ,OPTIONS => DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG + DBMS_LOGMNR.CONTINUOUS_MINE);

prompt alter system dump logfile '&&v_member' scn min &&v_curr1 scn max &&v_curr2;

alter system dump logfile '&&v_member' scn min &&v_curr1 scn max &&v_curr2;

--//執行指令碼a.txt:

xxxxxxxx> @ a.txt

System altered.

CURR1

------------

1336662128

100 rows updated.

Commit complete.

PL/SQL procedure successfully completed.

CURR2

------------

1336662131

exec DBMS_LOGMNR.START_LOGMNR(STARTSCN => 1336662128 ,ENDSCN => 1336662131 ,OPTIONS => DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG + DBMS_LOGMNR.CONTINUOUS_MINE)

alter system dump logfile '+DATA/ORCLCDB/ONLINELOG/group_2.264.985030477' scn min 1336662128 scn max 1336662131

System altered.

xxxxxxxx> @ viewsess redo%size

NAME STATISTIC# VALUE SID

---------------------------------- ---------- -------------- ------------

redo size 293 23692 258

redo size for lost write detection 295 0 258

redo size for direct writes 296 0 258

redo write size count ( 4KB) 321 0 258

redo write size count ( 8KB) 322 0 258

redo write size count ( 16KB) 323 0 258

redo write size count ( 32KB) 324 0 258

redo write size count ( 64KB) 325 0 258

redo write size count ( 128KB) 326 0 258

redo write size count ( 256KB) 327 0 258

redo write size count ( 512KB) 328 0 258

redo write size count (1024KB) 329 0 258

redo write size count (inf) 330 0 258

IMU Redo allocation size 736 49012 258

14 rows selected.

--//日誌大小 23692-648 = 23044 ,大約22K.

--//如果你查詢轉儲檔案,你可以發現一個奇特的資訊,你根本找不到yyyy,zzzz相關的字串資訊.

--//也就是如果dml欄位前後兩者一樣,日誌根本沒有記錄.

3.修改dml語句重複測試:

$ cat a.txt

..

update t set v1=lpad('z',200,'z') ,v2=lpad('y',100,'y');

commit ;

...

--//執行a.txt

xxxxxxxx> @ viewsess redo%size

NAME STATISTIC# VALUE SID

---------------------------------- ---------- -------------- ----------

redo size 293 684 258

redo size for lost write detection 295 0 258

redo size for direct writes 296 0 258

redo write size count ( 4KB) 321 0 258

redo write size count ( 8KB) 322 0 258

redo write size count ( 16KB) 323 0 258

redo write size count ( 32KB) 324 0 258

redo write size count ( 64KB) 325 0 258

redo write size count ( 128KB) 326 0 258

redo write size count ( 256KB) 327 0 258

redo write size count ( 512KB) 328 0 258

redo write size count (1024KB) 329 0 258

redo write size count (inf) 330 0 258

IMU Redo allocation size 736 0 258

14 rows selected.

xxxxxxxx> @ a.txt

System altered.

CURR1

------------

1336662429

100 rows updated.

Commit complete.

PL/SQL procedure successfully completed.

CURR2

------------

1336662432

exec DBMS_LOGMNR.START_LOGMNR(STARTSCN => 1336662429 ,ENDSCN => 1336662432 ,OPTIONS => DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG + DBMS_LOGMNR.CONTINUOUS_MINE)

alter system dump logfile '+DATA/ORCLCDB/ONLINELOG/group_3.262.985030477' scn min 1336662429 scn max 1336662432

System altered.

xxxxxxxx> @ viewsess redo%size

NAME STATISTIC# VALUE SID

---------------------------------- ---------- -------------- ------------

redo size 293 73948 258

redo size for lost write detection 295 0 258

redo size for direct writes 296 0 258

redo write size count ( 4KB) 321 0 258

redo write size count ( 8KB) 322 0 258

redo write size count ( 16KB) 323 0 258

redo write size count ( 32KB) 324 0 258

redo write size count ( 64KB) 325 0 258

redo write size count ( 128KB) 326 0 258

redo write size count ( 256KB) 327 0 258

redo write size count ( 512KB) 328 0 258

redo write size count (1024KB) 329 0 258

redo write size count (inf) 330 0 258

IMU Redo allocation size 736 36236 258

14 rows selected.

--//日誌大小73948-648 = 73300,至少72K,比原來增加不少.

--//你可以看到如下:

REDO RECORD - Thread:1 RBA: 0x0008b3.0000002c.0134 LEN: 0x00e0 VLD: 0x01 CON_UID: 1

SCN: 0x000000004fabd870 SUBSCN: 2 11/16/2018 10:30:36

CHANGE #1 CON_ID:1 TYP:0 CLS:24 AFN:4 DBA:0x010008de OBJ:4294967295 SCN:0x000000004fabd870 SEQ:96 OP:5.1 ENC:0 RBL:0 FLG:0x0000

ktudb redo: siz: 68 spc: 866 flg: 0x0022 seq: 0x0ba1 rec: 0x69

xid: 0x0004.004.00002086

ktubu redo: slt: 4 rci: 104 opc: 11.1 objn: 104890 objd: 104890 tsn: 0

Undo type: Regular undo Undo type: Last buffer split: No

Tablespace Undo: No

0x00000000

KDO undo record:

KTB Redo

op: 0x02 ver: 0x01

compat bit: 4 (post-11) padding: 1

op: C uba: 0x010008de.0ba1.68

KDO Op code: LKR row dependencies Disabled

ktudb redo: siz: 68 spc: 656 flg: 0x0022 seq: 0x0ba1 rec: 0x6c

op: F xid: 0x0006.00d.00002131 uba: 0x010000c8.0b0c.01

Block cleanout record, scn: 0x000000004fabd99d ver: 0x01 opt: 0x02 bigscn: Y compact: Y spare: 00000000, entries follow...

itli: 3 flg: (opt=2 whr=1) scn: 0x000000004fabd871

Array Update of 20 rows:

tabn: 0 slot: 0(0x0) flag: 0x2c lock: 1 ckix: 0

ncol: 3 nnew: 2 size: 0

KDO Op code: 21 row dependencies Disabled

xtype: XAxtype KDO_KDOM2 flags: 0x00000080 bdba: 0x0041af39 hdba: 0x0041af38

itli: 1 ispac: 0 maxfr: 4863

vect = 3

col 1: [200]

7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a 7a

col 2: [100]

79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79

tabn: 0 slot: 1(0x1) flag: 0x2c lock: 1 ckix: 0

4.修改dml語句重複測試:

$ cat a.txt

..

update t set v1=lpad('z',200,'z') ,v2=lpad('x',100,'x');

commit ;

...

--//v1欄位修改前後一樣,v2欄位前後不同,開始是lpad('y',100,'y')後面變成lpad('x',100,'x').

xxxxxxxx> @ viewsess redo%size

NAME STATISTIC# VALUE SID

----------- ---------- -------------- ----------

redo size 293 684 258

....

xxxxxxxx> @ a.txt

System altered.

CURR1

------------

1336662656

100 rows updated.

Commit complete.

PL/SQL procedure successfully completed.

CURR2

------------

1336662659

exec DBMS_LOGMNR.START_LOGMNR(STARTSCN => 1336662656 ,ENDSCN => 1336662659 ,OPTIONS => DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG + DBMS_LOGMNR.CONTINUOUS_MINE)

alter system dump logfile '+DATA/ORCLCDB/ONLINELOG/group_1.265.985030477' scn min 1336662656 scn max 1336662659

System altered.

xxxxxxxx> @ viewsess redo%size

NAME STATISTIC# VALUE SID

--------- ---------- -------------- ------------

redo size 293 48340 258

....

--//日誌大小48340-648 = 47692,47K上下.

--//檢查跟蹤檔案你可以發現:

REDO RECORD - Thread:1 RBA: 0x0008b5.0000005f.0040 LEN: 0x01d0 VLD: 0x01 CON_UID: 1

SCN: 0x000000004fabda80 SUBSCN:1176 11/16/2018 10:44:53

CHANGE #1 CON_ID:1 TYP:0 CLS:18 AFN:4 DBA:0x01000087 OBJ:4294967295 SCN:0x000000004fabda80 SEQ:27 OP:5.1 ENC:0 RBL:0 FLG:0x0000

ktudb redo: siz: 188 spc: 3282 flg: 0x0022 seq: 0x0b4d rec: 0x1b

xid: 0x0001.002.000020c9

ktubu redo: slt: 2 rci: 26 opc: 11.1 objn: 104890 objd: 104890 tsn: 0

Undo type: Regular undo Undo type: Last buffer split: No

Tablespace Undo: No

0x00000000

KDO undo record:

KTB Redo

op: 0x02 ver: 0x01

compat bit: 4 (post-11) padding: 1

op: C uba: 0x01000087.0b4d.1a

KDO Op code: URP row dependencies Disabled

xtype: XA flags: 0x00000000 bdba: 0x0041af3d hdba: 0x0041af38

itli: 2 ispac: 0 maxfr: 4863

tabn: 0 slot: 7(0x7) flag: 0x2c lock: 0 ckix: 0

ncol: 3 nnew: 1 size: 0

col 2: [100]

79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79 79

CHANGE #2 CON_ID:1 TYP:0 CLS:1 AFN:1 DBA:0x0041af3d OBJ:104890 SCN:0x000000004fabda80 SEQ:8 OP:11.5 ENC:0 RBL:0 FLG:0x0000

KTB Redo

op: 0x02 ver: 0x01

compat bit: 4 (post-11) padding: 1

op: C uba: 0x01000087.0b4d.1b

KDO Op code: URP row dependencies Disabled

xtype: XA flags: 0x00000000 bdba: 0x0041af3d hdba: 0x0041af38

itli: 2 ispac: 0 maxfr: 4863

tabn: 0 slot: 7(0x7) flag: 0x2c lock: 2 ckix: 0

ncol: 3 nnew: 1 size: 0

col 2: [100]

78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78

--//沒有字元z相關內容(7a 7a).

5.總結:

--//你可以發現oracle 18c在dml下修改欄位前後如果資訊不變,日誌根本沒有記錄,這樣一定程度減少日誌大小.

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/267265/viewspace-2220303/，如需轉載，請註明出處，否則將追究法律責任。

[20181116]18c DML 日誌優化.txt

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