Oracle10g 有一項新功能稱為：自動的基於磁碟的備份與恢復( Automatic Disk-Based Backup and Recovery )。實現該功能的基礎為本文要講述的閃回恢復區( FlashRecovery Area )。閃回恢復區是 Oracle 10g 中的新事物。簡單的說，閃回恢復區是一塊用以儲存恢復相關的檔案的儲存空間。

如果資料庫採用歸檔模式，那麼預設情況下歸檔檔案也會產生在閃回區裡面.

SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 9
Next log sequence to archive 11
Current log sequence 11

SQL> show paramter db_recovery_file_dest

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string /oracle10/flash_recovery_area
db_recovery_file_dest_size big integer 512M
recovery_parallelism integer 0

如果此時更改log_archive_dest引數，將會報錯(意思是log_archive_dest和db_recovery_file_dest不能同時使用)：

SQL> alter system set log_archive_dest='/oracle10/archive_test/';
alter system set log_archive_dest='/oracle10/archive_test/'
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-16018: cannot use LOG_ARCHIVE_DEST with LOG_ARCHIVE_DEST_n or
DB_RECOVERY_FILE_DEST

不過可以透過更改spfile來更改log_archive_dest
SQL> alter system set log_archive_dest='/oracle10/archive_test/' scope=spfile;

System altered.

然後重啟資料庫，經過測試，發現此時歸檔會產生到log_archive_dest和db_recovery_file_dest兩個目錄，且檔名根據各自不同的風格

如果想停用閃回區，可以這樣修改:

SQL> alter system set db_recovery_file_dest='' scope=spfile;

System altered.

然後重啟資料庫，此時歸檔後可以發現，歸檔檔案已經不在閃回區裡產生了，只會在log_archive_dest裡面產生

SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /oracle10/archive_test/
Oldest online log sequence 17
Next log sequence to archive 19
Current log sequence 19

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10g閃回區和歸檔目錄的關係

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