Connecting to a Database

Use the Database Connection Properties dialog box to create or customize a database connection.

Connection Types

Direct Connection

Direct mode does not require an Oracle Client to be installed on your workstation. dbForge Data Compare for Oracle talks to the Oracle server directly, no third party libraries are required.

You can connect to a multi-threaded server using Direct mode. The server must be configured to use a specific port and TTC protocol. This can help you avoid firewall conflicts.

Direct mode advantages:

  • Installation and administration of an Oracle Client are not required
  • System requirements are reduced

Direct mode restrictions:

  • Database export and import operations with Export and Import Utility wizards are not supported
  • Oracle RAC (Real Application Clusters) is not supported
  • OS authentication feature is not available
  • TCP/IP protocol connection only


You can return to a connection via an TNS at any time if restrictions above become critical for you.

Connection via the TNS

The TNS connection type is an appropriate option in any of the following circumstances:

  • You have an Oracle client installed on your machine.
  • You have access to many Oracle Database instances.
  • You do not know the machine details of the system hosting the Oracle Database instance you want to connect to.

A TNS connection uses an alias entry from a tnsnames.ora file. dbForge Data Compare for Oracle uses only one tnsnames.ora file. You may have more than one on your local machine or want to use the tnsnames.ora file on a remote machine, so note that dbForge Studio for Oracle looks sequentially for the tnsnames.ora file in the following locations:

  1. $HOME/.tnsnames.ora
  2. $TNS_ADMIN/tnsnames.ora
  3. /etc/tnsnames.ora (non-Windows systems)
  4. $ORACLE_HOME/network/admin/tnsnames.ora
  5. Registry key

You need to create the TNS_ADMIN environment variable in the case when the tnsnames.ora file exists but dbForge Data Compare for Oracle doesn’t use it.


Data Compare for Oracle uses connection via an TNS by default.

Connection via TNS Using OS Authentication

With OS authentication, Oracle Database uses a database user’s OS login credentials to authenticate that user. The user doesn’t provide a username or password to access the database, and Oracle Database doesn’t store and manage the account password. Local OS authentication can be used when the client and the database server are on the same machine. Remote OS authentication is possible but is not considered secure.