When trying to connect to a database using Toad for Oracle on a Windows 7 64-bit or Windows Server 2003 2008 64-bit operating system, the following error occurs:
Can't initialize OCI. Error -1
The Oracle client installed is a 32-bit Oracle client.
Right-click the Toad for Oracle shortcut and select "Run as Administrator" to avoid the error.
Right-click the Toad for Oracle shortcut | Properties | Compatibility Tab | check mark "Run this program in compatibility mode for" | choose "Windows XP Service Pack 3" from the drop-down list.
Right-click My Computer | Properties | Advanced tab | Environment Variables | under ‘System Variables’ (lower part) | check if you have an entry for ORACLE_HOME. If yes, rename it to ORACLE_HOME_OLD, and then re-test the issue.
Upgrade your Oracle client to a version that is 10.2.0.4 or later, preferably 11g.
Uninstall your Toad and re-install in 'C:\Quest Software\' instead of the default folder location.
For other common Oracle connection problems in Toad for Oracle 10.5 and above, please review SOL64853
Toad for Oracle
9.7.2, 9.6.1, 8.6.1, 126.96.36.199, 12.0, 11.6.1, 10.6.1
Created on: 3/19/2010
Last Update on: 7/3/2013