ORA-19909(一次DataGuard Failover导致的故障

      某医院客户，核心数据库有两个备库。因想将其中一个备库主机挪作测试使用，所以，想把数据库切换成读写模式。这样，就涉及到了做备库的failover动作。这个failover是在另外一个备库，主库都存活的情况下进行的。      Faiover进行得很顺利。Failover之后，修改了此数据库的DG的几个参数，当天以为事情就这么完了。       第二日，客户告知另一个备库的数据没有同步。于是登录过去，看到告警日志中有如下错误       MRP0: Incarnation has changed! Retry recovery... Errors in file /oradata/u01/app/diag/rdbms/orcldg/orcl/trace/orcl_pr00_3272.trc: ORA-19906: recovery target incarnation changed during recovery Managed Standby Recovery not using Real Time Apply Recovery interrupted! Recovered data files to a consistent state at change 19274002051 Tue Jun 09 16:37:39 2020  started logmerger process Tue Jun 09 16:37:39 2020 Managed Standby Recovery starting Real Time Apply Warning: Recovery target destination is in a sibling branch of the controlfile checkpoint. Recovery will only recover changes to datafiles. Datafile 1 (ckpscn 19274002051) is orphaned on incarnation#=3 MRP0: Detected orphaned datafiles!  Recovery will possibly be retried after flashback... Errors in file /oradata/u01/app/diag/rdbms/orcldg/orcl/trace/orcl_pr00_27714.trc: ORA-19909: datafile 1 belongs to an orphan incarnation ORA-01110: data file 1: '/oradata/datafile/system01.dbf' 通过RMAN查看incarnation connected to target database: ORCL (DBID=1385973181) RMAN> list incarnation; using target database control file instead of recovery catalog List of Database Incarnations DB Key  Inc Key DB Name  DB ID            STATUS  Reset SCN  Reset Time ------- ------- -------- ---------------- --- ---------- ---------- 1       1       ORCL     1385973181       PARENT  1          13-SEP-14 2       2       ORCL     1385973181       PARENT  4733207525 12-FEB-15 3       3       ORCL     1385973181       CURRENT 8619762801 08-JUL-17 4       4       ORCL     1385973181       ORPHAN  19273953428 09-JUN-20 其中incarnation 4正是昨天做failover产生的。解决起来其实也相对较为简单：reset database incarnation to 3;然后在开启日志应用即可Wed Jun 10 11:10:26 2020RFS[5]: Assigned to RFS process 19310RFS[5]: Allowing overwrite of partial archivelog for thread 2 sequence 40151RFS[5]: Opened log for thread 2 sequence 40151 dbid 1385973181 branch 948759254Completed: alter database recover managed standby database using current logfile disconnectArchived Log entry 72765 added for thread 2 sequence 40151 rlc 948759254 ID 0x5d2e975e dest 2:Media Recovery Log /oradata/arch/2_40151_948759254.dbfMedia Recovery Waiting for thread 1 sequence 1748Archivelog record exists, but no file is foundRFS[5]: Opened log for thread 1 sequence 36160 dbid 1385973181 branch 948759254Archived Log entry 72766 added for thread 1 sequence 36160 rlc 948759254 ID 0x5d2e975e dest 2:MRP0: Log being waited on was inappropriate for recovery. Retry recovery...Errors in file /oradata/u01/app/diag/rdbms/orcldg/orcl/trace/orcl_pr00_19224.trc:ORA-16426: Recovery requested an incorrect log from which to apply redo data.Managed Standby Recovery not using Real Time ApplyWed Jun 10 11:10:34 2020Recovery interrupted!Wed Jun 10 11:10:54 2020 started logmerger processWed Jun 10 11:10:55 2020Managed Standby Recovery starting Real Time ApplyParallel Media Recovery started with 16 slavesWaiting for all non-current ORLs to be archived...All non-current ORLs have been archived.Media Recovery Log /oradata/arch/2_40151_948759254.dbfMedia Recovery Log /oradata/arch/1_36160_948759254.dbfMedia Recovery Log /oradata/arch/2_40152_948759254.dbfMedia Recovery Log /oradata/arch/1_36161_948759254.dbf 此次故障，应当在做failover之前修改主备库的DG相关参数。作为数据库工程师，应该考虑更为周全。幸而影响范围较小。