发生错误如下，源端EXTRACT进程异常中止，查看日志，发现如下错误。

2014-07-23 01:32:13  ERROR   OGG-00446  Oracle GoldenGate Capture for Oracle, ext_mkt.prm:  Could not find archived log for sequence 74730 thread 1 under default destinations SQL , error retrieving redo file name for sequence 74730, archived = 1, use_alternate = 0Not able to establish initial position for sequence 74730, rba 32190992.

到归档目录查看序列号为74730的归档已经被删除，

解决办法：

从备份文件恢复归档

restore archivelog low logseq 74730;