1.sqlplus / as sysdba后使用select instance_name,status from v$instance后出错：
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
进程 ID: 0
会话 ID: 0 序列号: 0
解决办法：先关闭，然后重新启动
$ export ORACLE_SID=YOUR_TARGET_ORACLE_INSTANCE $ sqlplus / as sysdba >shutdown immediate; >startup;
原文：http://www.cnblogs.com/wrencai/p/4368625.html