Toad is unable to make new connections or sessions after a certain period of time since Toad was launched or started. New connections fail with ORA-12154 error. SQL Plus can make a new connection to the same database. Toad will have to be restarted or open a second Toad instance to make a new connection.
It has been seen in the past; installing and using an Oracle Client 11g R2 (instead of 10g client) resolved the issue. The Oracle Client 11g R2 was also acquired directly from the Oracle download site, not from the customer's intranet or internal sites
Below are the actions needed to acquire the proper Oracle client and Toad for Oracle client per the Toad Release Notes.
Uninstall the Oracle 10g client.
Uninstall the Toad for Oracle client via Start | All Programs | Quest Software | Uninstall Quest Products. Follow the steps in the wizard.
Download the Oracle and Toad clients
Please use the link below and follow the step to install the oracle 11gr2 32-bit client:
32-bit Oracle 11g R2 Client – Download Link:
Oracle Database 11g Release 2 Client (11.2.0.1.0)
for Microsoft Windows (32-bit)
File name is: win32_11gR2_client.zip (684,581,290 bytes)
Click here for the 32 bit 11g Oracle client
1. - Ensure that your Windows User has Administrator Rights before installing an Oracle Client (or Toad).
2. - Toad for Oracle supports 32-bit Oracle Clients only. Do NOT install any 64-bit Oracle Clients.
3. –Unzip the file and run the Set.exe file. During the Oracle Client installation, choose “Full” or “Administrator” installation type (this is not automatically selected).
Follow the wizard to complete the installation.
Also, you should upgrade your Toad for Oracle to the current release as well.
The 10.5 version is no longer supported.
Click here to get to the Toad for Oracle 32 bit Base edition.
Click here for the Toad for Oracle 32 bit client
