1. 如果没有备份机制，想要实现备库归档自动删除，就需要使用快速恢复区(FRA)

  检查当前备库归档的存放位置：

SQL> show parameter log_archive_dest_1

NAME     TYPE    VALUE

------------------------------------ ---------------------- ------------------------------

log_archive_dest_1     string    location=/archdir valid_for=(ALL_LOGFILES,ALL_ROLES) DB_UNIQUE_NAME=standby

2. 更改FRA配置

ALTER SYSTEM SET db_recovery_file_dest_size=60g SCOPE=BOTH;

ALTER SYSTEM SET db_recovery_file_dest=/archdir SCOPE=BOTH;

ALTER SYSTEM SET log_archive_dest_1='location=USE_DB_RECOVERY_FILE_DEST valid_for=(ALL_LOGFILES, ALL_ROLES) DB_UNIQUE_NAME=standby' SCOPE=BOTH;

3. 重启备库

ALTER DATABASE RECOVER  managed standby database cancel;

shutdown immediate

startup mount

ALTER DATABASE RECOVER  managed standby database disconnect from session;

此时alert里显示新的archivelog存放到FRA里

 Media Recovery Log /archdir/STANDBY/archivelog/2017_07_13/o1_mf_2_265_dpgfvl3o_.arc

4. 配置rman的归档删除策略

 CONFIGURE ARCHIVELOG DELETION POLICY TO APPLIED ON STANDBY;

当FRA空间达到80%使用率时，就会自动删除已经应用的archivelog： 

 Deleted Oracle managed file /archdir/STANDBY/archivelog/2017_07_18/o1_mf_2_412_dpvh6d5d_.arc