如何启用Oracle10g闪回数据库特性
1.确认当前模式
SYS AS SYSDBA on 29-MAR-05 >select flashback_on from v$database;
FLA
---
NO
2.检查/修改恢复区设置
SYS AS SYSDBA on 29-MAR-05 >show parameter db_recovery_file_dest
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string /data5/flash_recovery_area
db_recovery_file_dest_size big integer 10G
3.检查/修改闪回时间设置
SYS AS SYSDBA on 29-MAR-05 >show parameter db_flashback_retention_target
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_flashback_retention_target integer 60
SYS AS SYSDBA on 29-MAR-05 >alter system set db_flashback_retention_target=1440;
System altered.
4.重新启动数据库到Mount状态
启动flashback database选项。
SYS AS SYSDBA on 29-MAR-05 >shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SYS AS SYSDBA on 29-MAR-05 >startup mount;
ORACLE instance started.
Total System Global Area 314572800 bytes
Fixed Size 1301704 bytes
Variable Size 261890872 bytes
Database Buffers 50331648 bytes
Redo Buffers 1048576 bytes
Database mounted.
SYS AS SYSDBA on 29-MAR-05 >alter database flashback on;
Database altered.
SYS AS SYSDBA on 29-MAR-05 >alter database open;
Database altered.
数据库 宕机 查询：
SQL> select sid,event,p1,p1text from v$session_wait;
出现：
1570 Streams AQ: qmn slave idle wait
1631 Streams AQ: waiting for time management or cleanup tasks
1636 Streams AQ: 0qmn coordinator idle wait
各位 大哥 能不能给个建议
haha(137403441) 2010-04-13 11:56:16
宕机？看看告警日志呢？
Waits on event "log file sync" while performing COMMIT and ROLLBACK operations
were consuming significant database time.
RATIONALE: The average size of writes to the online redo log files was
15 K and the average time per write was 29 milliseconds.
是不是要加大redo啊？
提交太快
但不提交页不行啊
解决方案:
1.提高LGWR性能
尽量使用快速磁盘，不要把redo log file存放在raid 5的磁盘上
2.使用批量提交
3.适当使用NOLOGGING/UNRECOVERABLE等选项
同意 so的办法
來源：http://itlife365.com/?post=213