2016年3月8日，接到某综合网管系统负责人申告，该系统RMAN备份失败，RMAN备份失败日志如下：
操作系统:REDHAT linux 5.6
数据库版本：11.2.0.3
channel ORA_DISK_1: starting piece 1 at 07-MAR-16
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 03/07/2016 11:36:24
ORA-19809: limit exceeded for recovery files
ORA-19804: cannot reclaim 67108864 bytes disk space from 4322230272 limit
continuing other job steps, job failed will not be re-run
channel ORA_DISK_1: starting compressed full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
including current SPFILE in backup set
channel ORA_DISK_1: starting piece 1 at 07-MAR-16
channel ORA_DISK_1: finished piece 1 at 07-MAR-16
piece handle=/opt/ora_install/fast_recovery_area/CSWG/backupset/2016_03_07/o1_mf_ncsnf_TAG20160307T112117_cfsxssb7_.bkp tag=TAG20160307T112117 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of backup command on ORA_DISK_1 channel at 03/07/2016 11:36:24
ORA-19809: limit exceeded for recovery files
ORA-19804: cannot reclaim 67108864 bytes disk space from 4322230272 limit
这个问题较明显，问题原因就是数据库的RMAN备份路径指定到了闪回区，经过与系统负责人沟通发现RMAN备份脚本没有指定备份路径，所以备份就写到闪回区了。
通过下面命令查询当前数据库的闪回区目录，可以发现闪回区目录下，Oracle允许存放的文件空间确实很小，是默认的4G
SQL> show parameter db_recovery_file;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest string /opt/ora_install/fast_recovery_area
db_recovery_file_dest_size big integer 4122M
查看闪回区目录存放的文件信息，可以发现，闪回目录下只有一个1MB的备份集，并没有达到4G，通过SQLPLUS查询也能印证。
[oracle][/opt/ora_install/fast_recovery_area/CSWG/backupset/2016_03_04]$ls -al
total 0
drwxr-x--- 2 oracle oinstall 256 Mar 04 00:14 .
drwxr-x--- 4 oracle oinstall 256 Mar 07 11:21 ..
-rw-r----- 1 oracle oinstall 1114112 Mar 04 00:14 o1_mf_ncsnf_TAG20160304T000004_cfjrq8r2_.bkp
SQL> select * from v$recovery_file_dest;
NAME SPACE_LIMIT SPACE_USED SPACE_RECLAIMABLE NUMBER_OF_FILES
------------------------------------------- ----------- ---------- ----------------- ---------------
/opt/ora_install/fast_recovery_area 4322230272 2211840
这一点比较有意思，如果闪回区满，通过rm -rf删除闪回区目录下的文件，ORACLE数据库还是会不停的告警闪回目录满，其实需要我们到rman工作台执行删除备份集及归档同步catalog库记录信息。
[oracle][/opt/ora_install/fast_recovery_area/CSWG/backupset/2016_03_04]$rman target /
Recovery Manager: Release 11.2.0.3.0 - Production on Tue Mar 8 09:33:11 2016
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
connected to target database:**** (DBID=3404523328)
RMAN> crosscheck archivelog all ;
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=2280 device type=DISK
validation failed for archived log
archived log file name=/opt/ora_log/1_167_905310595.dbf RECID=3 STAMP=905401082
validation failed for archived log
archived log file name=/opt/ora_log/1_168_905310595.dbf RECID=1 STAMP=905401081
validation failed for archived log
.
.
.
validation succeeded for archived log
archived log file name=/opt/ora_log/1_642_905310595.dbf RECID=476 STAMP=905937113
Crosschecked 476 objects
RMAN> delete archivelog all;
released channel: ORA_DISK_1
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=2280 device type=DISK
List of Archived Log Copies for database with db_unique_name CSWG
=====================================================================
Key Thrd Seq S Low Time
------- ---- ------- - ---------
3 1 167 X 02-MAR-16
Name: /opt/ora_log/1_167_905310595.dbf
Do you really want to delete the above objects (enter YES or NO)? yes
deleted archived log
archived log file name=/opt/ora_log/1_167_905310595.dbf RECID=3 STAMP=905401082
deleted archived log
.
.
.
deleted archived log
archived log file name=/opt/ora_log/1_643_905310595.dbf RECID=477 STAMP=905938535
Deleted 477 objects
RMAN> exit
Recovery Manager complete.
还有一个解决方法，就是调大闪回区的空间限制，增加db_recovery_file_dest_size，需要注意的是需要重启数据库。
SQL> startup mount;
.
.
SQL> alter system set db_recovery_file_dest_size=20G;
System altered.
SQL> alter database open;
Database altered.