What line needs to be added to sqlnet.ora to enable connections through an HTTP proxy?

The correct line to be added to the sqlnet.ora file to enable connections through an HTTP proxy is SQLNET.USE_HTTPS_PROXY=ON. This setting specifically informs the Oracle client to utilize an HTTP proxy for secure connections, which is essential for establishing communication in environments where direct connections are not possible due to network restrictions or firewall configurations.

Using this directive enables the Oracle client to correctly route traffic through the specified HTTP proxy, ensuring that data can be securely transmitted over the internet. This is particularly important for applications and services that require secure communication when connecting to Oracle databases.

Other options may not achieve the desired effect; they either imply different functionalities or serve other connection protocols that do not specifically address the use of an HTTP proxy for database connections. Thus, SQLNET.USE_HTTPS_PROXY=ON is the appropriate choice for enabling HTTP proxy connections effectively.