There may be many reasons for why you cannot connect to a database, but some of the most common are:

• Incorrect values for the Database Server or Database Port fields in the Object View tab for the connection,
• TCP/IP access is not enabled in the database server,
• A firewall between the client and the database server blocks connections to the database port,
• A syntax error in a manually entered JDBC URL,
• The user account is not authorized to connect from the client where you run DbVisualizer,
• Native libraries for a JDBC driver are not found.

The first three problems usually results in a somewhat cryptic message about I/O errors or a time-out. You can use the Ping Server button to make sure that the a TCP/IP network connection can be established to the specified server and port. If this test fails, please ask your system or database administrator for help.

JDBC syntax errors typically result in one of two error messages:

• "The selected Driver cannot handle the specified Database URL. The most common reason for this error is that the database URL contains a syntax error preventing the driver from accepting it. The error also occurs when trying to connect to a database with the wrong driver. Correct this and try again."
• "java.sql.SQLException: Io exception: Invalid number format for port number Io exception: Invalid number format for port number"

In both cases, we recommend using the Server Info settings format instead of the Database URL format for the connection, and let DbVisualizer build a valid JDBC URL for you. If you must enter a JDBC URL manually, make sure that you replace possible placeholders enclosed with "<" and ">" in a template you have copied, such as <1521>, and look for other syntax errors. Also verify that the JDBC driver is installed correctly.

Authorization problems are usually described by more straight forward messages. Ask you database administrator to help you get it resolved.

If you get a message about native libraries not being found, e.g. "no ocijdbc11 in java.library.path" or similar, it is because you have not installed these in a location where DbVisualizer can read them. Unless you have a very good reason for using a JDBC driver that requires native code, we recommend that you use a pure Java JDBC driver (a Type 4 driver) instead, like the "Oracle Thin" driver for Oracle.

If none of this helps, please contact us using the Help->Contact Support form. Most of the information we can gather about the problem is typically already filled in, but please add any additional details that may help us figure out what is wrong.