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 <SELECT name FROM v$archived_log WHERE sequence# = :ora_seq_no AND thread# = :ora_thread AND resetlogs_id = :ora_resetlog_id AND archived = 'YES' AND deleted = 'NO' AND name not like '+%' AND standby_dest = 'NO' >, 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;