Oracle 64-bit PL/SQL connection error Make sure you have the 32 B... oracle OraDb11g_home 64-bit under Windows 64-bit server. PLSQL Developer has the following problems: 1. The Database drop-down box is blank. 2. Enter the user name, password, and Database. The logon prompt is displayed: initialation error cocould not initialize ".... "Make sure you have the 32 bits Oracle Client installed. oracleHomeKey: OracleHomeDir :... found: oci. dll Using :... loadlibrary (...) returned 0 indicates that PLSQL Developer does not support Oracle 64-bit client connection. Solution: 1. Install a 32-bit Oracle client. 2. Set PLSQL Developer to start PLSQL Developer without logging in. Tools> Preferences: Oracle Home: OraDb11g_home1 OCI Library: D: \ oracle \ product \ 11.2.0 \ client_1 \ oci. dll 3. Add the environment variable TNSADMIN-> D: \ ORACLE \ product \ 11.2.0 \ dbhome1 \ NETWORK \ ADMIN