Oracle通過SCN做增量備份修復DG

　　DG由於網絡原因或者bug原因經常不同步，有時隔得時間久了，就會丟失歸檔日志，或者長時間的歸檔恢復較慢，有一種可以基於scn的方式來恢復DG庫，使用基於scn的增量備份來恢復standby庫可以節省大量時間，或者進行dg異常的重新同步。

　　1，查詢主庫和備庫的scn，redo號等信息，選取合適的scn號進行主庫的備份

--查詢DG端最低的scn，以下查詢結果應該相同
 select to_char(current_scn) scn from v$database;
 select min(fhscn) from x$kcvfh;

 select distinct to_char(checkpoint_change#) from v$datafile_header order by 1; 

--以歸檔日志查詢相關scn
 select THREAD#,min(sequence#) from v$archived_log where applied='NO' group by THREAD#;  
 select THREAD#,max(sequence#) from v$archived_log where applied='NO' group by THREAD#; 

 SELECT thread#,SEQUENCE#,to_char(FIRST_CHANGE#) fc,to_char(NEXT_CHANGE#) nc FROM v$archived_log WHERE SEQUENCE# = 32995 ORDER BY 1,2; 

　　2，主庫端基於scn的增量備份

RMAN> BACKUP INCREMENTAL FROM SCN <SCN from previous step> 
DATABASE FORMAT '/tmp/ForStandby_%U' tag 'FORSTANDBY'
--or
  backup device type disk incremental from scn 11125946510 database format'/home/oracle/db_incre%U.bbk'; 
--or
run {
allocate channel t1 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
allocate channel t2 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
allocate channel t3 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
allocate channel t4 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
allocate channel t5 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
allocate channel t6 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
allocate channel t7 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
allocate channel t8 type 'sbt_tape' parms 'ENV=(NB_ORA_CLIENT=bossb1)';
backup incremental from scn 12844051683640 database format 'forstandby_%u' tag 'forstandby';
backup current controlfile for standby format 'forstandbyctrl.bck' tag 'forstandby_cnt'; 
  release channel t1;
  release channel t2;
  release channel t3;
  release channel t4;
  release channel t5;
  release channel t6;
  release channel t7;
  release channel t8;
}

 ALTER DATABASE CREATE standby controlfile AS '/home/oracle/standby.ctl';  

　　3，傳輸文件到dg端，rman catalog start with

　　4，恢復控制文件，恢復數據庫

RMAN>restore controlfile from'/data/oracle/backup/restore/standby.ctl';    
--mount database
RMAN> RECOVER DATABASE NOREDO;

　　5，啟動同步進程，檢查同步狀態等。