Specifying Alternate Destinations

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Specifying Alternate Destinations

To specify that a location be an archive destination only in the event of a failure of another destination, you can make it an alternate destination. Both local and remote destinations can be alternates. The following example makes LOG_ARCHIVE_DEST_4 an alternate for LOG_ARCHIVE_DEST_3:

ALTER SYSTEM SET LOG_ARCHIVE_DEST_4 = 'LOCATION=/disk4/arch';ALTER SYSTEM SET LOG_ARCHIVE_DEST_3 = 'LOCATION=/disk3/arch MAX_FAILURE=1   ALTERNATE=LOG_ARCHIVE_DEST_4';ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_4=ALTERNATE;SQL> SELECT dest_name, status, destination FROM v$archive_dest; DEST_NAME               STATUS    DESTINATION----------------------- --------- ----------------------------------------------LOG_ARCHIVE_DEST_1      VALID     /disk1/archLOG_ARCHIVE_DEST_2      VALID     /disk2/archLOG_ARCHIVE_DEST_3      VALID     /disk3/archLOG_ARCHIVE_DEST_4      ALTERNATE /disk4/arch

通过测试：ALTER SYSTEM SET LOG_ARCHIVE_DEST_2 = 'LOCATION=G:\testb' scope=spfile;ALTER SYSTEM SET LOG_ARCHIVE_DEST_1 = 'LOCATION=F:\test\a NOREOPEN MAX_FAILURE=1 ALTERNATE=LOG_ARCHIVE_DEST_2' scope=spfile;ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=ALTERNATE  scope=spfile;shut immediate;startupSQL> show parameter log_archive_dest_NAME                                 TYPE        VALUE------------------------------------ ----------- ------------------------------log_archive_dest_1                   string      LOCATION=I:\test  MANDATORY  M                                                 AX_FAILURE=1 ALTERNATE=LOG_ARC                                                 HIVE_DEST_2log_archive_dest_2                   string      LOCATION=F:\test1  MANDATORYSQL> select dest_id,dest_name,status,destination,REOPEN_SECS,failure_count,max_failure from v$archive_dest where dest_name in ('LOG_ARCHIVE_DEST_1','LOG_ARCHIVE_DEST_2');   DEST_ID DEST_NAME                                          STATUS    DESTINATION                                REOPEN_SECS FAILURE_COUNT MAX_FAILURE---------- -------------------------------------------------- --------- -------------------------------------------------- ----------- ------------- -----------         1 LOG_ARCHIVE_DEST_1                                 VALID     I:\test                                            300             0           1         2 LOG_ARCHIVE_DEST_2                                 ALTERNATE F:\test1                                           300             0           0alter system switch logfile;切换n个 log；alter system switch logfile;I:\test 所在的盘i盘撑满继续切换日志alter system switch logfile;可以发现日志切换到了   F:\test1   盘我们可以查看日志目录的状态：SQL> select dest_id,dest_name,status,destination,REOPEN_SECS,failure_count,max_failure from v$archive_dest where dest_name in ('LOG_ARCHIVE_DEST_1','LOG_ARCHIVE_DEST_2');   DEST_ID DEST_NAME                                          STATUS    DESTINATION                                REOPEN_SECS FAILURE_COUNT MAX_FAILURE---------- -------------------------------------------------- --------- -------------------------------------------------- ----------- ------------- -----------         1 LOG_ARCHIVE_DEST_1                                 DISABLED  I:\test                                            300             1           1         2 LOG_ARCHIVE_DEST_2                                 VALID     F:\test1                                           300             0           0在I盘满后，如果要切换回原来的LOG_ARCHIVE_DEST_1 为主盘，LOG_ARCHIVE_DEST_2 为备盘，可以切换alter system set  LOG_ARCHIVE_DEST_STATE_1=ENABLE;alter system set  LOG_ARCHIVE_DEST_STATE_2=ALTERNATE;SQL> select dest_id,dest_name,status,destination,REOPEN_SECS,failure_count,max_failure from v$archive_dest where dest_name in ('LOG_ARCHIVE_DEST_1','LOG_ARCHIVE_DEST_2')   DEST_ID DEST_NAME                                          STATUS    DESTINATION                                REOPEN_SECS FAILURE_COUNT MAX_FAILURE---------- -------------------------------------------------- --------- -------------------------------------------------- ----------- ------------- -----------         1 LOG_ARCHIVE_DEST_1                                 VALID     I:\test                                            300             1           1         2 LOG_ARCHIVE_DEST_2                                 ALTERNATE F:\test1                                           300             0           0然后再切日志alter system switch logfile; 归档又会切到LOG_ARCHIVE_DEST_1 地址

相关参数：location   配置本地归档位置service   配置远程归档位置（即DG）mandatory   必须成功归档到指定路径之后，redo日志才能被复用。备库上慎用optional   可选的归档目标，如果归档失败，放弃归档reopen=n   归档失败后重试周期，默认值300秒AFFIRM—specifies that a redo transport destination acknowledges received redo data after writing it to the standby redo log.NOAFFIRM—specifies that a redo transport destination acknowledges received redo data before writing it to the standby redo log.

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