Oracle E-Business Suite Release 11.5.10 introduced support for the Oracle Net security feature, tcp.validnode_checking, which is used to prevent unauthorized Oracle Net access (for example via SQL*Plus) to the Applications database. If a node or PC is not registered, the connection attempt will fail with the error ORA-12537: TNS: connection closed.在sqlnet.ora文件中将tcp.validnode_checking的值设为no。然后重启数据库与服务就可以了。[转]楼主看看是不是这个问题
把你的sqlnet.ora也上传上来看看
不是RAC,单实例的,服务器客户端都没有用到sqlnet.ora文件。