关于v$backup_redolog中next_change#列

关于v$backup_redolog中next_change#列

next_change#列实际上就是下一个日志序列号的first_change#。
在rac环境（假设是两个节点的rac）中进行recover时，
需要在每个thread中选择出日志序列号最大的那个日志序列号，
然后在这两个日志序列号之间进行比较，比较的依据是next_change#，选择较小的那个next_change#作为recover的终点，比如如下的例子：

SQL> select max(sequence#) from v$archived_log L, v$database D
     where L.resetlogs_change# = D.resetlogs_change# and thread#=1;

       MAX(SEQUENCE#)
       --------------
               25 ----------->thread# 1的已经归档的最大日志序列号是25

SQL> select max(sequence#) from v$archived_log L, v$database D
     where L.resetlogs_change# = D.resetlogs_change# and thread#=2;

       MAX(SEQUENCE#)
       --------------
             13   ----------->thread# 2的已经归档的最大日志序列号是13

 SQL> select sequence#, thread#, first_change#, next_change#
      from v$archived_log L, v$database D
      where L.resetlogs_change# = D.resetlogs_change# and
      sequence# in (13,25);

      SEQUENCE#    THREAD# FIRST_CHANGE# NEXT_CHANGE#
     -------------------- -------------- ------------------------- -------------------------
                            25            1                           1744432                    1744802
                            13            2                           1744429                    1744805

SQL> select sequence#, thread#, first_change#, next_change#
     from v$backup_redolog
     where sequence# in (13,25);

      SEQUENCE#    THREAD# FIRST_CHANGE# NEXT_CHANGE#
      -------------------- -------------- ------------------------- -------------------------
                            25            1                           1744432                    1744802
                            13            2                           1744429                    1744805

由于1744802<1744805,因此 recover的终点是thread# 1的最大日志序列号25,也就是：

SET UNTIL SEQUENCE 26 THREAD 1;

 

如上摘自：

HowTo Restore RMAN Disk backups of RAC Database to Single Instance On Another Node (文档 ID 415579.1)