关于集成抽取进程重启后的现象分析

当执行一个大的事务或数据量比较大时，停止集成抽取进程ex1，发现不能停止，然后直接kill，此时，再start ex1，发现ex1是running状态，但checkpoint lag一直在增加，也获取不到SCN。然后再

kill ex1,

alter ex1, begin now,

start ex1,

info ex1

查看之后，仍然是相同的情况。

GGSCI (WIN7ora as src_ogg@orcl) 407> info ex1 EXTRACT EX1 Last Started 2017-11-29 09:23 Status RUNNING Checkpoint Lag 00:00:10 (updated 00:00:08 ago) Process ID 3854 Log Read Checkpoint Oracle Integrated Redo Logs 2017-11-29 09:24:02 SCN 0. (0)

经分析，应该是集成抽取的读取点有记录在DB的某个系统表里，造成，即使修改begin now，也不起作用。经查找ogg reference文档，有看到如下一段说明

发现即使alter ex1, begin now之后，上面的first scn也未变化，所以此参数无法调整抽取进程的读取点，即不能跳过某些日志或事务。

简单的delete进程之后，重新add extract，结果相同。

最终，将进程unregister extract ex1 database之后，再重新register，first scn有发生变化。

GGSCI (WIN7ora as src_ogg@orcl) 407> info ex1 EXTRACT EX1 Last Started 2017-11-29 10:23 Status RUNNING Checkpoint Lag 00:00:10 (updated 00:00:08 ago) Process ID 3856 Log Read Checkpoint Oracle Integrated Redo Logs 2017-11-29 14:58:42 SCN 0.6794325 (6794325)

停止进程提示处于recovery状态

GGSCI (WIN7ora as src_ogg@orcl) 408> stop ex1 Sending STOP request to EXTRACT EX1 ... STOP request pending. Recovery is not complete. This normal stop will wait and checkpoint recovery's work when recovery has finished. To force Extract to stop now, use the SEND EXTRACT EX1, FORCESTOP command..

GGSCI (WIN7ora as src_ogg@orcl) 409> info ex1 EXTRACT EX1 Last Started 2017-11-29 10:23 Status RUNNING Checkpoint Lag 00:00:09 (updated 00:00:01 ago) Process ID 3856 Log Read Checkpoint Oracle Integrated Redo Logs 2017-11-29 14:59:04 SCN 0.6794344 (6794344)

GGSCI (WIN7ora as src_ogg@orcl) 406> send ex1, status Sending STATUS request to EXTRACT EX1 ... EXTRACT EX1 (PID 3856) Current status: In recovery[1]: Processing data Current read position: Redo thread #: 1 Sequence #: 0 RBA: 0 Timestamp: 2017-11-29 09:50:36.000000 SCN: 0.0 (0) Current write position: Sequence #: 0 RBA: 0 Timestamp: 2017-11-29 10:23:14.560000 Extract Trail: ./dirdat/ea

GGSCI (WIN7ora as src_ogg@orcl) 432> send ex1, status Sending STATUS request to EXTRACT EX1 ... EXTRACT EX1 (PID 1304) Current status: In recovery[1]: Processing data Current read position: Redo thread #: 1 Sequence #: 3221 RBA: 7516312 Timestamp: 2017-11-29 14:59:13.000000 SCN: 0.6794348 (6794348) Current write position: Sequence #: 0 RBA: 0 Timestamp: 2017-11-29 10:23:14.560000 Extract Trail: ./dirdat/ea

GGSCI (WIN7ora as src_ogg@orcl) 439> send ex1, status Sending STATUS request to EXTRACT EX1 ... EXTRACT EX1 (PID 2528) Current status: Recovery complete: Processing data Current read position: Redo thread #: 1 Sequence #: 3221 RBA: 9566584 Timestamp: 2017-11-29 15:01:06.000000 SCN: 0.6794877 (6794877) Current write position: Sequence #: 45 RBA: 3074 Timestamp: 2017-11-29 15:01:05.188000 Extract Trail: ./dirdat/ea

Ref: https://community.oracle.com/thread/3490542