flash recovery area配置
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检查数据库是否开启闪回:
SQL> select flashback_on from v$database;FLASHBACK_ON------------------------------------YES
打开闪回区,必须要将数据库在mount阶段才能开启,否则会报错,如下:
SQL> alter database flashback on;alter database flashback on*ERROR at line 1:ORA-38759: Database must be mounted by only one instance and not open.
打开闪回区,数据库必须在归档模式下,否则会报错,如下:
SQL> alter database flashback on;alter database flashback on*ERROR at line 1:ORA-38706: Cannot turn on FLASHBACK DATABASE logging.ORA-38707: Media recovery is not enabled.
将数据库修改为归档模式:
SQL> alter database archivelog;Database altered
在mount阶段,在归档模式下,打开闪回区:
SQL> alter database open;Database altered.
查看数据库能闪回到最早的SCN:
SQL> select oldest_flashback_scn,oldest_flashback_time from v$flashback_database_log;OLDEST_FLASHBACK_SCN OLDEST_FLASH-------------------- ------------ 648133 13-JUL-14
查看配置的基本参数:
SQL> show parameter db_recovery_fileNAME TYPE VALUE------------------------------------ -------- ------------------------------db_recovery_file_dest string +RECOVERdb_recovery_file_dest_size big inte 2G ger
数据库可以恢复到多少分钟前的,默认是一天
SQL> show parameter flashNAME TYPE VALUE------------------------------------ -------- ------------------------------db_flashback_retention_target integer 1440
使用flash back area需要在初始化参数中定义两个参数,db_recovery_file_dest定义的是闪回区的位置,db_recovery_file_dest_size定义的是闪回区的大小,在RAC环境下配置时,需要保证每个节点的值是相同的:
修改这两个参数的时候,可以在线进行修改,如下:
SQL> alter system set db_recovery_file_dest = '+ASM' scope=both;System altered.SQL> alter system set db_recovery_file_dest_size='5g' scope=both sid='*';System altered.
在使用ASM作为闪回区的位置时,只能指定到磁盘组级别,而不能是某个目录,因为ASM使用的是OMF进行管理的,会自动进行目录的创建:
SQL> alter system set db_recovery_file_dest='+recovery/test' scope=both;alter system set db_recovery_file_dest='+recovery/test' scope=both*ERROR at line 1:ORA-02097: parameter cannot be modified because specified value is invalidORA-01261: Parameter db_recovery_file_dest destination string cannot betranslatedSQL> alter system set db_recovery_file_dest='+recovery' scope=both;System altered.
监控闪回区空间的大小使用情况:
SQL> col name format a32 heading 'file name'SQL> col spc_lmt_mb format 9999.99 heading 'space|limit|(mb)'SQL> col spc_usd_mb format 9999.99 heading 'space|limit|(mb)' SQL> col spc_rcl_mb format 9999.99 heading 'reclm|space|(mb)'SQL> col spc_usd_mb format 9999.99 heading 'space|used|(mb)'SQL> col number_of_files format 99999 heading 'files'SQL> select name,space_limit/(1024*1024) spc_lmt_mb,space_used/(1024*1024) spc_usd_mb,space_reclaimable/(1024*1024) spc_rcl_mb,number_of_files from v$recovery_file_dest; space space reclm limit used spacefile name (mb) (mb) (mb) files-------------------------------- -------- -------- -------- ------+recovery 5120.00 165.20.00 5
如果空间使用率到达85%,在alert日志中可以看到waring的日志,如果超过了97%,会记录一条critical warning日志。告警日志查看:
SQL> select reason,object_type,suggested_action from dba_outstanding_alerts;
查看是什么文件占用了空间:
SQL> select * from v$flash_recovery_area_usage;FILE_TYPE PERCENT_SPACE_USED PERCENT_SPACE_RECLAIMABLE files------------------------ ------------------ ------------------------- ------CONTROLFILE.13 0 1ONLINELOG 2.93 0 3ARCHIVELOG 0 0 0BACKUPPIECE 0 0 0IMAGECOPY 0 0 0FLASHBACKLOG.15 0 16 rows selected.
在oracle11g的默认情况下,归档日志是保存在flash back area中的,因此如果空间不够,那么将会造成归档日志无法归档,从而删除过期的归档日志即可:
使用RMAN删除过期归档日志:
[oracle@kel ~]$ rman target /Recovery Manager: Release 10.2.0.1.0 - Production on Mon Jul 14 00:08:02 2014Copyright (c) 1982, 2005, Oracle. All rights reserved.connected to target database: OMF (DBID=680034237)RMAN> crosscheck archivelog all;using target database control file instead of recovery catalogallocated channel: ORA_DISK_1channel ORA_DISK_1: sid=154 devtype=DISKvalidation succeeded for archived logarchive log filename=+RECOVER/omf/1_1_852236226.dbf recid=1 stamp=852320500validation succeeded for archived logarchive log filename=+RECOVER/omf/1_2_852236226.dbf recid=2 stamp=852423499validation succeeded for archived logarchive log filename=+RECOVER/omf/1_3_852236226.dbf recid=3 stamp=852579011validation succeeded for archived logarchive log filename=+RECOVER/omf/1_4_852236226.dbf recid=4 stamp=852840609Crosschecked 4 objectsRMAN> delete expired archivelog all;released channel: ORA_DISK_1allocated channel: ORA_DISK_1channel ORA_DISK_1: sid=154 devtype=DISKspecification does not match any archive log in the recovery catalog
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