Create Database Links from Autonomous Database to a Publicly Accessible Autonomous Database

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

See How to Create a Database Link from Your Autonomous Database to a Database Cloud Service Instance for more information.

Create Database Links from Autonomous Database to a Publicly Accessible Autonomous Database without a Wallet (TLS)
You can create database links from an Autonomous Database to a publicly accessible Autonomous Database without a wallet (TLS).
Create Database Links from Autonomous Database to a Publicly Accessible Autonomous Database with a Wallet (mTLS)
You can to create database links from an Autonomous Database to a publicly accessible Autonomous Database with a wallet (mTLS).

Parent topic: Create Database Links from Autonomous Database to Another Autonomous Database

Create Database Links from Autonomous Database to a Publicly Accessible Autonomous Database without a Wallet (TLS)

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

To create database links to a public target, the target database must be accessible. Some databases, including Autonomous Databases, may limit access (for example, using Access Control Lists). Make sure you enable your target database to allow access from your source database for the database link to work. If you limit access with Access Control Lists (ACLs), you can find the outbound IP address of your source Autonomous Database and allow that IP address to connect to your target database. When the target database is another Autonomous Database, you can add the outbound IP address of the source database to the ACL of the target database.

See Obtain Tenancy Details for information on finding the outbound IP address.

To create a database link to a target Autonomous Database without a wallet (TLS):

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.
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.
Use the database link you created to access data on the target database.
For example:
```
SELECT * FROM employees@SALESLINK;
            
```

For the credentials you create in Step 1, the target database credentials, if the password of the target user changes you can update the credential that contains the target user's credentials as follows:

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

Where password is the new password.

After this operation, the existing database links that use this credential continue to work without having to drop and recreate the database links.

Note:

You can create links to Big Data Service using DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK. See Query Big Data Service Hadoop (HDFS) Data from Autonomous Database for more information.

For additional information, see:

Parent topic: Create Database Links from Autonomous Database to a Publicly Accessible Autonomous Database

Create Database Links from Autonomous Database to a Publicly Accessible Autonomous Database with a Wallet (mTLS)

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

To create database links to a public target, the target database must be accessible. Some databases, including Autonomous Databases, may limit access (for example, using Access Control Lists). Make sure you enable your target database to allow access from your source database for the database link to work. If you limit access with Access Control Lists (ACLs), you can find the outbound IP address of your source Autonomous Database and allow that IP address to connect to your target database. For example, if the target database is another Autonomous Database, you can add the outbound IP address of the source database to the ACL of the target database.

See Obtain Tenancy Details for information on finding the outbound IP address.

To create database links to a target Autonomous Database with a wallet (mTLS):

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.
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.
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.
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.
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.

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.

Use the database link you created to access data on the target database.
For example:
```
SELECT * FROM employees@SALESLINK;
            
```

For the credentials you create in Step 5, the target database credentials, if the password of the target user changes you can update the credential that contains the target user's credentials as follows:

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