What is the default port number for ATP?

The default port number for Oracle's Advanced Transaction Processing (ATP) is 1521. This port is commonly used by Oracle databases for network communications and is defined in the Oracle listener configuration, allowing client applications to connect to the database.

Port numbers are standardized to facilitate communication between different systems, and 1521 has been long established as the default for Oracle Database environments. The other port numbers listed do not serve as the default configuration for ATP in standard deployments, which is why 1521 is recognized as the correct answer in this context. Understanding this helps in configuring database connections effectively and troubleshooting connectivity issues in database management scenarios.