NBU恢复报错ORA-27211的解决
问题描述：
检查dataguard服务器的时候发现DG因为缺少归档停止应用了，alert日志里一直提示归档日志的lag。检查生产库备份集发现缺失的归档都有备份，于是写了恢复脚本准备从NBU（ver 7.7）中恢复一下缺失的归档日志。运行脚本的时候提示如下：
RMAN> run {
2> allocate channel ch1 device type 'sbt_tape'
3> PARMS="ENV=(MASTER_SERVER_IP=192.168.2.250,INSTANCE_NAME=xtcrm,BACKUP_CLIENT=CRM-Database,RESTORE_CLIENT=CRM-Database)";
4> restore archivelog from logseq 73709 until logseq 73732 thread 1;
5> release channel ch1;
6> }
released channel: ORA_DISK_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of allocate command on ch1 channel at 12/23/2020 22:06:06
ORA-19554: error allocating device, device type: SBT_TAPE, device name:
ORA-27211: Failed to load Media Management Library
Additional information: 2
经过咨询，发现主要的问题出在ORA-27211，检查$ORACLE_HOME/lib果然没有发现NBU的library链接文件，于是手工链接一个：
在$ORACLE_HOME/lib 目录下
libobk.so -> /usr/openv/netbackup/bin/libobk.so64
ln -s /usr/openv/netbackup/bin/libobk.so64 ./libobk.so
完成后，重新运行恢复归档脚本，正常。
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