在64位环境下用PL/SQL Developer连接:
1. 下载32位Oracle InstantClient,并展开到某目录,例如C:\instantclient-basic-nt-11.2.0.2.0;
2. 将系统的tnsnames.ora拷贝到该目录下;
3. 在PLSQL Developer中设置Oracle_Home和OCI Library: 
ToolsPreferencesOracleConnection:
Oracle_Home:	C:\instantclient-basic-nt-11.2.0.2.0
OCI Library:		C:\instantclient-basic-nt-11.2.0.2.0\oci.dll
4. 在PLSQL Developer目录下编辑如下,替换其快捷方式,启动PLSQL Developer:
@echo off
set path=C:\instantclient-basic-nt-11.2.0.2.0
set ORACLE_HOME=C:\instantclient-basic-nt-11.2.0.2.0
set TNS_ADMIN=C:\instantclient-basic-nt-11.2.0.2.0
set NLS_LANG=AMERICAN_AMERICA.ZHS16GBK
start plsqldev.exe