Duplicating Databases to Oracle Cloud
                        (Source: Oracle Docs)

Use the DUPLICATE command to duplicate an on-premise database to Oracle Cloud. 
Both backup-based and active duplication are supported.

Oracle databases on Oracle Cloud are always encrypted. 

Therefore, when you duplicate a database or part of a database to Oracle Cloud, any tablespaces created in Oracle Cloud are encrypted even if no encryption clause is specified during duplication.

The COMPATIBLE parameter of the source and Oracle Cloud database must be set to 18.0.0 or higher.

Ensure that the prerequisites for the selected duplication technique are met. It is recommended that you use active database duplication.

Configure the Oracle Database Cloud Backup Module. This backup module is an SBT interface that enables you to perform backup and recovery operations to Oracle Cloud.
See Oracle Cloud Using Oracle Database Backup Service for information about installing the Oracle Database Cloud Backup Module

Complete the planning tasks, as described in "Planning to Duplicate a Database".
Prepare the auxiliary instance with the following changes when duplicating CDBs:

    a. You must create the auxiliary instance as a CDB. To do so, start the instance with the following declaration in the        initialization parameter file:

        enable_pluggable_database=TRUE

    b. When instructed to create an initialization parameter file for the auxiliary instance, you must copy the file from        the source database. This ensures that the auxiliary instance is also a CDB. After you copy the file, perform the        following steps:

        1. Modify the DB_NAME parameter
        2. Modify the various destination/location parameters
        3. Start the auxiliary instance in NOMOUNT mode.

Note:

    a. Because the auxiliary instance must be created on Oracle Cloud
    b. The Oracle Cloud administrator must perform the steps to prepare the auxiliary instance.
    c. Start RMAN and connect to the root as a common user with the SYSDBA or SYSBACKUP privilege.
    d. On both the auxiliary instance and the target database, 
    e. the password for the user performing the duplication must be the same.
    f. master key is needed
        If     the source CDB uses encryption, 
        then 
            open the Oracle keystore that contains the master key on the source CDB.
        end

    g. Configure RMAN channels.
    h. The RMAN channels perform the primary task of duplication. 
    i. Configuring additional channels improves the duplication performance.
    j. On the destination CDB, open the Oracle keystore from the source CDB.
        If     the destination CDB uses a password-based software keystore, 
        then 
            you must specify the password used to open this keystore. 
        end
    k. The following command sets the password used to open a password-based software keystore 
       (replace password with your keystore password):
        
        SET DECRYPTION WALLET OPEN IDENTIFIED BY 'password';

Use the DUPLICATE command to duplicate the source CDB.

Note:Using duplication to create a standby database to Oracle Cloud is not supported.