This could be due to two different things:
- the listener isn't running (or isn't running on the port you think it is)
- the tnsnames.ora entry you're using isn't referencing the host and port where the listener is running
If you have a standalone computer with no network attached, then you may try setting an environment variable (ORACLE_SID) to the name of your Oracle database instance. Then, you should be able to connect without using a connect string since the ORACLE_SID variable will be used by default.
Dig Deeper on Oracle database installation, upgrades and patches
Related Q&A from Dan Norris
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.