今天用Oracle客户端连接服务端时，总是连接不上，错误信息：ORA-12637，问题解决如下：

找到 本地 SQLNET.ORA 文件

打开：

# sqlnet.ora Network Configuration File: F:\app\Administrator\product\11.2.0\client_1\network\admin\sqlnet.ora
# Generated by Oracle configuration tools.

# This file is actually generated by netca. But if customers choose to
# install "Software Only", this file wont exist and without the native
# authentication, they will not be able to connect to the database on NT.

SQLNET.AUTHENTICATION_SERVICES= (NTS)

NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)

将标红行去掉，即可连接成功，连接成功后，可以将其再添加回。