实验步骤：
1，制定一个重新抽取的SCN
2，根据SCN在v$archived_log视图找到起始时间
3，停止抽取进程
4，重置抽取进程的开始时间
5，启动抽取进程重新捕获事务（从归档日志中获取）
1，查看源端当前的SCN，记录该值作为重新抽取的时间点
SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
1507066
2，查看当前抽取进程ex1的状态
GGSCI (node3) 2> info ex1 detail
EXTRACT EX1 Last Started 2014-11-02 18:19 Status RUNNING
Checkpoint Lag 00:00:00 (updated 00:00:06 ago)
Log Read Checkpoint Oracle Redo Logs
2014-11-02 19:09:40 Thread 1, Seqno 12, RBA 10750464
SCN 0.1507682 (1507682)
Log Read Checkpoint Oracle Redo Logs
2014-11-02 19:09:39 Thread 2, Seqno 12, RBA 9300480
SCN 0.1507682 (1507682)
Target Extract Trails:
Remote Trail Name Seqno RBA Max MB
/goldengate/dirdat/ex 2 205729 5
Extract Source Begin End
+DATA/prod/onlinelog/group_4.302.859509357 2014-11-02 18:02 2014-11-02 19:09
Not Available * Initialized * 2014-11-02 18:02
Current directory /goldengate
Report file /goldengate/dirrpt/EX1.rpt
Parameter file /goldengate/dirprm/ex1.prm
Checkpoint file /goldengate/dirchk/EX1.cpe
Process file /goldengate/dirpcs/EX1.pce
Stdout file /goldengate/dirout/EX1.out
Error log /goldengate/ggserr.log
3，查看当前系统时间以及目前存在的local trail文件
[oracle@single goldengate]$ ls -l dirdat
total 424
-rw-rw-rw- 1 oracle oinstall 205826 Nov 1 16:02 rt000000
-rw-rw-rw- 1 oracle oinstall 1192 Nov 1 16:57 rt000001
-rw-rw-rw- 1 oracle oinstall 1161 Nov 1 17:20 rt000002
4，在源端节点2登录测试用户snow，向测试表插入100万条记录
SYS@PROD2 > conn snow/snow
SNOW@PROD2 > begin for i in 1001..1000000 loop
2 insert into t1 values(i,'Fin');
3 end loop;
4 commit;
5 end;
6 /
目标端snow.t1成功复制100万条记录
SQL> conn snow/snow
Connected.
SQL> select count(*) from t1;
COUNT(*)
----------
1000000
插入100条数据使得源端生成了22个local trail文件，从ex000003-ex000024
[oracle@node3 dirdat]$ ll
total 104128
-rw-rw-rw- 1 oracle oinstall 205795 Nov 2 17:24 ex000000
-rw-rw-rw- 1 oracle oinstall 1076 Nov 2 18:19 ex000001
-rw-rw-rw- 1 oracle oinstall 4999907 Nov 3 10:02 ex000003
-rw-rw-rw- 1 oracle oinstall 4999952 Nov 3 10:02 ex000004
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000005
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000006
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000007
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000008
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000009
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000010
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000011
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000012
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000013
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000014
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000015
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000016
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000017
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000018
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000019
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000020
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000021
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000022
-rw-rw-rw- 1 oracle oinstall 4999951 Nov 3 10:02 ex000023
-rw-rw-rw- 1 oracle oinstall 1122278 Nov 3 10:02 ex000024
5, 根据SCN1507066，查找相对应时间。
所在归档日志为红色表示记录。该日志生成的时间为2014-11-02 17:41:26，接下来采用该时间作为重新生成local trail的参数。