You can create database links from an Autonomous Database to a publicly accessible Autonomous Database without a wallet (TLS).

1. If you have not already done so, enable TLS connections on your Autonomous Database instance.

   See Update your Autonomous Database Instance to Allow both TLS and mTLS Authentication for details.

2. On the Autonomous Database instance where you are creating the database link, create credentials to access the target Autonomous Database. The username and password you specify with DBMS_CLOUD.CREATE_CREDENTIAL are the credentials for the target database (you use these credentials 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.

   Note
   
   You can use a vault secret credential for the target database credential in a database link. See Use Vault Secret Credentials for more information.

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

3. Create a database link to the target Autonomous Database instance 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 => '1521',
           service_name => 'example_medium.adb.example.oraclecloud.com',
           credential_name => 'DB_LINK_CRED',
           directory_name => NULL);
   END;
   /

   To create a database link with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK to a target Autonomous Database on a public endpoint using a secure TCP connection without a wallet, the directory_name parameter must be NULL.

   The ssl_server_cert_dn parameter can either be omitted or if included, specify a NULL value.

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

4. 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;
/

You can to create database links from an Autonomous Database to a publicly accessible Autonomous Database with a wallet (mTLS).

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.

   Creating a credential to access Oracle Cloud Infrastructure Object Store is not required if you enable resource principal credentials. See Use Resource Principal to Access Oracle Cloud Infrastructure Resources for more information.

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.

   Creating a credential to access Oracle Cloud Infrastructure Object Store is not required if you enable resource principal credentials. See Use Resource Principal to Access Oracle Cloud Infrastructure Resources for more information.

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.

   Note
   
   You can use a vault secret credential for the target database credential in a database link. See Use Vault Secret Credentials for more information.

   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.adb.example.oraclecloud.com',
           ssl_server_cert_dn => 'CN=adb.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;
/