Which encryption mode is used when migrating a schema with the ENCRYPTION parameter set to DATA_ONLY and the Oracle encryption wallet is open?

When migrating a schema with the ENCRYPTION parameter set to DATA_ONLY, the encryption mode used is Transparent Encryption. This mode facilitates the encryption of sensitive data without requiring changes to the applications that use the data. The use of an open Oracle encryption wallet indicates that the necessary encryption keys are accessible, allowing the data to be encrypted transparently during the migration process.

Transparent Encryption is designed to automatically encrypt data as it is written to the database and to decrypt it as it is read, ensuring that the data remains secure without interruption to user operations. Because the ENCRYPTION parameter specifies DATA_ONLY, it focuses specifically on the content of the data being migrated rather than the structure or schema itself.

In the context of the other options, Password encryption typically requires specific password provisions for each session, while Dual encryption involves both user and system operations needing to manage encryption keys accordingly. None indicates that no encryption method is applied, which contradicts the requirement for migration with encryption involved. Thus, the correct answer that reflects the appropriate encryption mode for this scenario is Transparent.