How can a customer behind a firewall connect to ADB?

The correct choice involves modifying the sqlnet.ora file, which is a configuration file used in Oracle database environments to define connection properties. By adding a specific line to this file, the customer can specify parameters that control how the database connection is established, particularly in scenarios where there are network security measures in place, such as firewalls.

In typical configurations, if an application or user is trying to connect to a database server that is behind a firewall, the connection may be blocked or restricted. Adjusting the sqlnet.ora file can help configure the necessary connection parameters to ensure that messages can appropriately traverse the firewall based on established rules or settings.

Using a VPN connection, while a secure method for remote access, doesn’t directly alter how the database connection is managed through sqlnet.ora; it simply provides a secure tunnel to the network. A direct database link, on the other hand, is a mechanism for a database to communicate with another database rather than a client connecting through a firewall. Disabling the firewall temporarily is a risky approach that exposes the system to security threats and is not advisable in a production environment. Thus, modifying the sqlnet.ora file correctly addresses the need for managing database connection settings amidst firewall policies.