When trying to contact my Oracle database, I get the following error through TOAD:
ORA-12514: TNS:listener could not resolve SERVICE_NAME given in connect descriptor
I have been using this database happily for months until now, when this has suddenly came up. Please tell me what might be going on here.
This error occurs when the SERVICE_NAME in your tnsnames.ora file (which is the most common naming method) isn't registered with the listener on the database server to which you're trying to connect. If your client configuration hasn't changed, then the database server configuration must have changed such that the SERVICE_NAME you had been using to connect is no longer being registered with the listener.
The SERVICE_NAME that is registered with the listener is determined by the service_names parameter for the database instance. Check the server documentation in the Reference Guide for details on how this parameter defaults if it isn't set. You may wish to explicitly set it to avoid it being impacted by changes to other parameters.
You may also be a victim of timing. If the listener is restarted, the database instance(s) will have to register with it again. This usually happens about every 60 seconds under normal conditions. If you can't wait for that, then logon to the database server as a DBA and run "alter system register;" to force it to register with the listener immediately.
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