问题：
SQL> conn system/123123@MECBS
ERROR:
ORA-12537: TNS:connection closed
Warning: You are no longer connected to ORACLE.
解决：
chmod 6751 $ORACLE_HOME/bin/oracle
Oracle 11gR2 RAC 数据库不能连接(ORA-12537TNS:connection closed)的解决
原文：http://7642644.blog.51cto.com/7632644/1576656