RMAN restore过程中报Cannot allocate memory
现象：
channel ORA_DISK_1: restoring datafile 00030 to +TESTDG/rac/datafile/users.292.817416403
channel ORA_DISK_1: reading from backup piece /UNID/full_eaope61n.bak
channel ORA_DISK_1: ORA-19870: error while restoring backup piece /UNID/full_eaope61n.bak
ORA-19501: read error on file "/UNID/full_eaope61n.bak", block number 6610944 (block size=8192)
ORA-27072: File I/O error
Linux-x86_64 Error: 12: Cannot allocate memory
Additional information: 4
Additional information: 6610944
Additional information: -1
failover to previous backup
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of restore command at 11/21/2013 17:21:50
RMAN-06026: some targets not found - aborting restore
RMAN-06023: no backup or copy of datafile 4 found to restore
连续几次都报Linux-x86_64 Error: 12: Cannot allocate memory
RMAN Restore脚本极其简单：
restore command: nohup rman target / cmdfile=/home/Oracle/rman log=/home/oracle/rman.log &
[oracle@rac1 ~]$ cat /home/oracle/rman
restore database;
[oracle@rac1 ~]$
分析：
1、RMAN原库与恢复目的库配置相差较大：
source:
[oracle@JOADBTEST01 ~]$ free -g
total used free shared buffers cached
Mem: 15 15 0 0 0 6
-/+ buffers/cache: 9 6
Swap: 17 1 15
target:
[root@rac1 ~]# free -g
total used free shared buffers cached
Mem: 3 3 0 0 0 2
-/+ buffers/cache: 0 3
Swap: 5 1 4
2、客户备份脚本非常简单：
cat backup.cmd
backup database;
没有限制backup piece大小，200多G的库最后只备份成了1个备份结果文件：
所有的备数据文件都备份到了一个大文件中，该文件大小为90多G。
诊断为：超大的备份结果文件和目的主机超低的配置导致了内存出现瓶颈，导致了RMAN无法继续工作，异常退出。
解决方法：
1.重新进行备份，限制backup piece大小为2G。
2.目的主机为虚拟机，调高配置。
推荐阅读：
RMAN 配置归档日志删除策略
Oracle基础教程之通过RMAN复制数据库
RMAN备份策略制定参考内容
RMAN备份学习笔记
Oracle数据库备份加密 RMAN加密