There are a lot of Oracle errors out there. Way too many, right?

Quick fix

To a database or other service a connection was requested using a connect identifier. The specified connection identifier could not be resolved to a connection descriptor by using one of the naming methods that are configured. As an example, if the type of connection identifier used was a network service name, the network service name could not be found in a naming method repository, or the repository could not be found or reached.

Best solution:

• https://docs.oracle.com/cd/B28359_01/server.111/b28278/net12150.htm#ORA-121504

Quick fix

A generic protocol adapter error occurred.

Hint:

Authenticate the addresses used for correct protocol specification. Before you report this error, look at the error stack and double-check for lower level transport errors. For more details, turn on tracing and perform the operation again. Turn off tracing when the operation is complete.

Best solution:

• https://docs.oracle.com/cd/B28359_01/server.111/b28278/net12500.htm#ORA-12560

Quick fix

The listener received a request to set up a connection to a database or other service. The connect descriptor that has been received by the listener specified a SID for an instance (usually a database instance). Either it has not been dynamically registered with the listener yet or has not been configured statically for the listener. This can be a temporary condition, for example, after the listener has been started, but before the database instance has registered with the listener.

Hint:

• Please wait a moment and try to reconnect.
• Find out which services are currently known by the listener by executing: lsnrctl services <listener name>
• Dopple-check that the SERVICE_NAME parameter in the connect descriptor of the net service name used specifies a service known to the listener.
• If an easy connect naming connect identifier was used, prove that the service name specified is a service known to the listener.
• Check in the listener.log file for an event

Best solution:

• https://docs.oracle.com/cd/B28359_01/server.111/b28278/net12500.htm#ORA-12500

Quick fix

The alert log is an XML file which is a chronological log of database messages and errors. It is stored in the ADR and contains messages on the following points:

• Critical errors (incidents)
• Administrative operations, such as starting or shutting down the database, restoring the database, creating or deleting a tablespace, and others.
• Error when automatically updating a materialized view
• Other database events

Hint:

View the alert log in text format (with the XML tags removed) using Enterprise Manager and the ADRCI utility. Also in the ADR there is a text-formatted version of the alarm log stored for backward compatibility. Having said that Oracle recommends that any parsing of the alert log contents can be done by using the XML-formatted version, as the text format is unstructured and can change from release to release.

Best solution:

• https://docs.oracle.com/cd/B28359_01/server.111/b28310/diag001.htm#ADMIN1126

More solutions:

• https://docs.oracle.com/cd/B28359_01/server.111/b28310/diag005.htm#ADMIN11267