了解GoldenGate Replicat的HANDLECOLLISIONS参数

HANDLECOLLISIONS是我们使用goldengate过程中常有的一个REPLICAT参数，该参数依赖于主键或唯一索引处理冲突数据，常用于初始化阶段。对于无主键或唯一索引的表无法处理冲突，且可能导致重复记录。注意打开此参数则所有数据错误不管reperror如何配置均不再写discard文件，即所有数据冲突信息被默认规则处理，没有任何日志(则会忽略error mapping数据错误，而且不会报告到discard文件)，因此日常复制不建议使用该参数；可予以考虑的特殊场景为只需新增数据，无需复制历史数据。

使用HANDLECOLLISIONS的几个场景：

target丢失delete记录(missing delete)，忽略该问题并不记录到discardfile
target丢失update记录(missing update)
- 更新的键值是主键=》 update转换成INSERT ，默认情况下插入记录不完整
- 更新的键值是非主键=》忽略该问题并不记录到discardfile
重复插入已存在的主键值到target表中，这将被replicat转换为UPDATE现有主键值的行的其他非主键列

情景1 target丢失delete记录(missing delete) ：

C:\Users\ML>sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Tue Sep 18 13:38:03 2012

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> conn sender/oracle
Connected.
SQL> create table handlec(t1 int primary key,t2 int);

Table created.

SQL> insert into handlec values(1,2);

1 row created.

SQL> insert into handlec values(3,2);

1 row created.

SQL> insert into handlec values(4,2);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from handlec;

        T1         T2
---------- ----------
         1          2
         3          2
         4          2

target :

SQL> conn receiver/oracle
Connected.
SQL> create table handlec(t1 int primary key,t2 int);

Table created.

SQL> insert into handlec values(1,2);

1 row created.

SQL> commit;

SQL> select * from handlec;

        T1         T2
---------- ----------
         1          2

SQL>

GGSCI (XIANGBLI-CN) 1> alter extract load2 , begin now
EXTRACT altered.

GGSCI (XIANGBLI-CN) 4> alter replicat rep2, begin now
REPLICAT altered.

GGSCI (XIANGBLI-CN) 13> add trandata sender.*

Logging of supplemental redo data enabled for table SENDER.HANDLEC.

Logging of supplemental redo log data is already enabled for table SENDER.TV.

GGSCI (XIANGBLI-CN) 14> start mgr
MGR is already running.

GGSCI (XIANGBLI-CN) 15> start er *

Sending START request to MANAGER ...
EXTRACT LOAD2 starting

Sending START request to MANAGER ...
REPLICAT REP2 starting

GGSCI (XIANGBLI-CN) 16> info all

Program     Status      Group       Lag at Chkpt  Time Since Chkpt

MANAGER     RUNNING
EXTRACT     RUNNING     LOAD2       00:00:00      00:00:01
REPLICAT    RUNNING     REP2        00:00:00      00:00:08

***SOURCE端删除一条TARGET没有的数据

SQL> delete handlec where t1=3;

1 row deleted.

SQL> commit;

Commit complete.

出现SQL error 1403错误，REPLICAT ABORT

2012-09-18 13:45:48  WARNING OGG-01004  Aborted grouped transaction on 'RECEIVER.HANDLEC', Database error 1403 (OCI Error ORA-01403: no data found, SQL ).

2012-09-18 13:45:48  WARNING OGG-01003  Repositioning to rba 1091 in seqno 3.

2012-09-18 13:45:48  WARNING OGG-01154  SQL error 1403 mapping SENDER.HANDLEC to RECEIVER.HANDLEC OCI Error ORA-01403: no data found, SQL .

2012-09-18 13:45:48  WARNING OGG-01003  Repositioning to rba 1091 in seqno 3.

Source Context :
  SourceModule            : [er.errors]
  SourceID                : [er/errors.cpp]
  SourceFunction          : [take_rep_err_action]
  SourceLine              : [623]
  ThreadBacktrace         : [8] elements
                          : [D:\ogg\V34342-01\gglog.dll(??1CContextItem@@UEAA@XZ+0x3272) [0x000000018010BDD2]]
                          : [D:\ogg\V34342-01\gglog.dll(?_MSG_ERR_MAP_TO_TANDEM_FAILED@@YAPEAVCMessage@@PEAVCSourceContext@@AEBV?$CQualDBObjName@$00@ggapp@gglib@ggs@@1W4MessageDisposition@CMessageFactory@@@Z+0x138) [0x00000001800AD508]]
                          : [D:\ogg\V34342-01\replicat.exe(ERCALLBACK+0x6e1e) [0x0000000140099D5E]]
                          : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x4411) [0x00000001400C9BE1]]
                          : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x289cd) [0x00000001400EE19D]]
                          : [D:\ogg\V34342-01\replicat.exe(CommonLexerNewSSD+0x9440) [0x00000001402AE980]]
                          : [C:\windows\system32\kernel32.dll(BaseThreadInitThunk+0xd) [0x000000007733652D]]
                          : [C:\windows\SYSTEM32\ntdll.dll(RtlUserThreadStart+0x21) [0x000000007746C521]]

2012-09-18 13:45:48  ERROR   OGG-01296  Error mapping from SENDER.HANDLEC to RECEIVER.HANDLEC.

***********************************************************************
*                   ** Run Time Statistics **                         *
***********************************************************************

Last record for the last committed transaction is the following: 
___________________________________________________________________
Trail name :  D:\ogg\V34342-01\ex\ze000003
Hdr-Ind    :     E  (x45)     Partition  :     .  (x04) 
UndoFlag   :     .  (x00)     BeforeAfter:     B  (x42) 
RecLength  :     9 (x0009)    IO Time    : 2012-09-18 13:45:38.000000  
IOType     :     3  (x03)     OrigNode   :   255  (xff)
TransInd   :     .  (x03)     FormatType :     R  (x52)
SyskeyLen  :     0  (x00)     Incomplete :     .  (x00)
AuditRBA   :         44       AuditPos   : 3337232
Continued  :     N  (x00)     RecCount   :     1  (x01)

2012-09-18 13:45:38.000000 Delete             Len     9 RBA 1091
Name: SENDER.HANDLEC
___________________________________________________________________

Reading D:\ogg\V34342-01\ex\ze000003, current RBA 1091, 0 records

Report at 2012-09-18 13:45:48 (activity since 2012-09-18 13:45:48)

From Table SENDER.HANDLEC to RECEIVER.HANDLEC:
       #                   inserts:         0
       #                   updates:         0
       #                   deletes:         0
       #                  discards:         1

Last log location read:
     FILE:      D:\ogg\V34342-01\ex\ze000003
     SEQNO:     3
     RBA:       1091
     TIMESTAMP: 2012-09-18 13:45:38.000000
     EOF:       NO
     READERR:   0

2012-09-18 13:45:48  ERROR   OGG-01668  PROCESS ABENDING.

2012-09-18 13:45:48  INFO    OGG-01237  Trace file D:\ogg\V34342-01\REP_TRACE1.TRC closed.

2012-09-18 13:45:48  INFO    OGG-01237  Trace file D:\ogg\V34342-01\REP_TRACE2.TRC closed.

CACHE OBJECT MANAGER statistics

CACHE MANAGER VM USAGE
vm current     =      0    vm anon queues =      0 
vm anon in use =      0    vm file        =      0 
vm used max    =      0    ==> CACHE BALANCED

CACHE CONFIGURATION
cache size       =   2G   cache force paging = 3.41G
buffer min       =  64K   buffer highwater   =   8M
pageout eligible size =   8M

================================================================================

使用skiptransaction跳过上述失败事务

GGSCI (XIANGBLI-CN) 18> start rep2 skiptransaction

Sending START request to MANAGER ...
REPLICAT REP2 starting

情景2 target丢失update记录(missing update)，更新的键值是主键：

继续我们的测试, 针对source的某条记录进行更新

SQL> update handlec set t1=5 where t1=4;

1 row updated.

SQL> commit;

Commit complete.

对于在target 丢失更新(miss update)的情况也会造成 Database error 1403+OGG-01296

2012-09-18 13:49:30  WARNING OGG-01004  Aborted grouped transaction on 'RECEIVER.HANDLEC', Database error 1403 (OCI Error ORA-01403: no data found, SQL <UPDATE "RECEIVER"."HANDLEC" SET "T1" = :a1 WHERE "T1" = :b0>).

2012-09-18 13:49:30  WARNING OGG-01003  Repositioning to rba 1218 in seqno 3.

2012-09-18 13:49:30  WARNING OGG-01003  Repositioning to rba 1218 in seqno 3.

Source Context :
  SourceModule            : [er.errors]
  SourceID                : [er/errors.cpp]
  SourceFunction          : [take_rep_err_action]
  SourceLine              : [623]
  ThreadBacktrace         : [8] elements
                          : [D:\ogg\V34342-01\gglog.dll(??1CContextItem@@UEAA@XZ+0x3272) [0x000000018010BDD2]]
                          : [D:\ogg\V34342-01\gglog.dll(?_MSG_ERR_MAP_TO_TANDEM_FAILED@@YAPEAVCMessage@@PEAVCSourceContext@@AEBV?$CQualDBObjName@$00@ggapp@gglib@ggs@@1W4MessageDisposition@CMessageFactory@@@Z+0x138) [0x00000001800AD508]]
                          : [D:\ogg\V34342-01\replicat.exe(ERCALLBACK+0x6e1e) [0x0000000140099D5E]]
                          : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x4411) [0x00000001400C9BE1]]
                          : [D:\ogg\V34342-01\replicat.exe(shutdownMonitoring+0x289cd) [0x00000001400EE19D]]
                          : [D:\ogg\V34342-01\replicat.exe(CommonLexerNewSSD+0x9440) [0x00000001402AE980]]
                          : [C:\windows\system32\kernel32.dll(BaseThreadInitThunk+0xd) [0x000000007733652D]]
                          : [C:\windows\SYSTEM32\ntdll.dll(RtlUserThreadStart+0x21) [0x000000007746C521]]

2012-09-18 13:49:30  ERROR   OGG-01296  Error mapping from SENDER.HANDLEC to RECEIVER.HANDLEC.

加入HANDLECOLLISIONS后，rep可以继续工作且不生成discard记录

GGSCI (XIANGBLI-CN) 23> view params rep2
replicat rep2
userid receiver , password oracle
trace ./rep_trace1.trc
trace2 ./rep_trace2.trc
ASSUMETARGETDEFS
HANDLECOLLISIONS
map sender.*, target receiver.*;

GGSCI (XIANGBLI-CN) 18> start rep2

SQL> select * from handlec;

        T1         T2
---------- ----------
         1          2
         5

这里出现T1=5 T2 NULL记录的原因是，丢失update的更新操作是针对主键的更新，此时replicat会尝试插入一条记录而非忽略该update。
注意插入的记录可能不是完整的行，如上例中的T2 为NULL ，若要求完整的行记录则要求EXTRACT使用PKUPDATE选项。

需要加入的选项是FETCHOPTIONS FETCHPKUPDATECOLS

将以上选项加入到EXTRACT参数文件中，并重启EXTRACT。这将引起extract捕获完整的主键更新镜像。

如以下的例子：

SQL> conn receiver/oracle
Connected.
SQL> select * from handlec;

T1 T2
---------- ----------
1 2
10 100
5
20 200

SQL> delete handlec where t1=5;

1 row deleted.

SQL> commit;

Commit complete.

SQL> select * from handlec;

T1 T2
---------- ----------
1 2
10 100
20 200

SQL> conn sender/oracle
Connected.

SQL> update handlec set t1=t1+1000 where t1=5;

1 row updated.

SQL> commit;

Commit complete.

SQL> conn receiver/oracle
Connected.
SQL>
SQL>
SQL> select * from handlec;

T1 T2
---------- ----------
1 2
10 100
20 200
1005 2

如上述实验验证FETCHOPTIONS FETCHPKUPDATECOLS将捕获完整的redo image镜像到trail中，这保证把primary key的更新通过HANDLECOLLISIONS转换为对target的一个完整记录的插入。

情景3 重复插入已存在的主键值到target表中，这将被replicat转换为UPDATE现有主键值的行的其他非主键列：

*** TARGET 

SQL> conn receiver/oracle
Connected.

SQL> select * from handlec;

        T1         T2
---------- ----------
         1          2
        10          9
		 5

target中已经存在 t1=10 t2=9的记录 ，此时再在source中插入(10,100)的记录

>>SOURCE

SQL> insert into handlec values(10,100);

1 row created.

SQL> commit;

>>TARGET

SQL> select * from handlec;

        T1         T2
---------- ----------
         1          2
        10        100
         5

上面可以看到在source的insert操作，因为在target中已有对应的主键记录所以被启用HANDLECOLLISIONS的REPLICAT转换为UPDATE非主键的其他COLUMNS

总结

HANDLECOLLISIONS是我们使用goldengate过程中常有的一个REPLICAT参数，该参数依赖于主键或唯一索引处理冲突数据，常用于初始化阶段。对于无主键或唯一索引的表无法处理冲突，且可能导致重复记录。注意打开此参数则所有数据错误不管reperror如何配置均不再写discard文件，即所有数据冲突信息被默认规则处理，没有任何日志，因此日常复制不建议使用该参数；可予以考虑的特殊场景为只需新增数据，无需复制历史数据。

使用HANDLECOLLISIONS的几个场景：

target丢失delete记录(missing delete)，忽略该问题并不记录到discardfile
target丢失update记录(missing update)
- 更新的键值是主键=》 update转换成INSERT ，默认情况下插入记录不完整
- 更新的键值是非主键=》忽略该问题并不记录到discardfile
重复插入已存在的主键值到target表中，这将被replicat转换为UPDATE现有主键值的行的其他非主键列

另：该参数仅处理数据本身的Insert/Delete冲突，如果出现两端映射或其它结构性问题Replicat进程依然会abend，不能被忽略

此外对于主键的更新操作，若在target使用HANDLECOLLISIONS且该update丢失，在会转换为INSERT该主键的操作，注意默认情况下插入的记录不完整，FETCHOPTIONS FETCHPKUPDATECOLS将捕获完整的redo image镜像到trail中，这保证把primary key的更新通过HANDLECOLLISIONS转换为对target的一个完整记录的插入。

我们可以通过send 命令动态取消HANDLECOLLISIONS

GGSCI (XIANGBLI-CN) 29> send rep2, NOHANDLECOLLISIONS

Sending NOHANDLECOLLISIONS request to REPLICAT REP2 ...
REP2 NOHANDLECOLLISIONS set for 1 tables and 0 wildcard entries

了解GoldenGate Replicat的HANDLECOLLISIONS参数

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