You can create database links from an Autonomous Database to a target Oracle database that is on a public endpoint.

1. Copy your target database wallet, cwallet.sso, containing the certificates for the target database to Object Store.

   Note the following for the wallet file:

   • The wallet file, along with the Database user ID and password provide access to data in the target Oracle Database. Store wallet files in a secure location. Share wallet files only with authorized users.

   • Do not rename the wallet file. The wallet file in Object Storage must be named cwallet.sso.

2. Create credentials to access your Object Store where you store the wallet file cwallet.sso. See CREATE_CREDENTIAL Procedure for information about the username and password parameters for different object storage services.
3. Create a directory on Autonomous Database for the wallet file cwallet.sso.

   For example:

   CREATE DIRECTORY dblink_wallet_dir AS 'directory_path_of_your_choice';
               

   See Create Directory in Autonomous Database for information on creating directories.

4. Use DBMS_CLOUD.GET_OBJECT to upload the target database wallet to the directory you created in the previous step, DBLINK_WALLET_DIR.

   For example:

   BEGIN 
       DBMS_CLOUD.GET_OBJECT(
           credential_name => 'DEF_CRED_NAME',
           object_uri => 'https://objectstorage.us-phoenix-1.oraclecloud.com/n/namespace-string/b/bucketname/o/cwallet.sso',
           directory_name => 'DBLINK_WALLET_DIR'); 
   END;
   /

   In this example, namespace-string is the Oracle Cloud Infrastructure object storage namespace and bucketname is the bucket name. See Understanding Object Storage Namespaces for more information.

   Note
   
   The credential_name you use in this step is the credentials for the Object Store. In the next step you create the credentials to access the target database.
5. On the Autonomous Database instance, create credentials to access the target database. The username and password you specify with DBMS_CLOUD.CREATE_CREDENTIAL are the credentials for the target database that you use to create the database link.
   Note
   
   Supplying the credential_name parameter is required.

   For example:

   BEGIN
       DBMS_CLOUD.CREATE_CREDENTIAL(
           credential_name => 'DB_LINK_CRED',
           username => 'NICK',
           password => 'password');
   END;
   /

   The characters in the username parameter must be all uppercase letters.

   This operation stores the credentials in the database in an encrypted format. You can use any name for the credential name.

6. Create the database link to the target database using DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK.

   For example:

   BEGIN
       DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
           db_link_name => 'SALESLINK',
           hostname => 'adb.eu-frankfurt-1.oraclecloud.com', 
           port => '1522',
           service_name => 'example_medium.atpc.example.oraclecloud.com',
           ssl_server_cert_dn => 'CN=atpc.example.oraclecloud.com,OU=Oracle BMCS FRANKFURT,O=Oracle Corporation,L=Redwood City,ST=California,C=US',
           credential_name => 'DB_LINK_CRED',
           directory_name => 'DBLINK_WALLET_DIR');
   END;
   /

   Users other than ADMIN require privileges to run DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK.

   If the wallet file in the directory specified with directory_name is not cwallet.sso, the procedure reports an error such as: ORA-28759: failure to open file.

7. Use the database link you created to access data on the target database.

   For example:

   SELECT * FROM employees@SALESLINK;
               

BEGIN
    DBMS_CLOUD.UPDATE_CREDENTIAL (
        credential_name => 'DB_LINK_CRED',
        attribute => 'PASSWORD',
        value => 'password' );
END;
/

• Database Link Notes with a Target Oracle Database
  Provides notes for creating database links to a target Oracle database (when the target is not an Autonomous Database)