Create Database Links to an Oracle Database that is not an Autonomous Database

You can create database links from an Autonomous Database to an Oracle database that is on a private endpoint or on a public endpoint (publicly accessible).

Note:

See Create Database Links from Autonomous Database to Another Autonomous Database if the target for your database link is another Autonomous Database.

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

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

To use database links with Autonomous Database the target database must be configured to use TCP/IP with SSL (TCPS) authentication. Autonomous Databases use TCP/IP with SSL (TCPS) authentication by default, so you do not need to do any additional configuration in your target database to link to another Autonomous Database. Other Oracle databases must be configured to use TCP/IP with SSL (TCPS) authentication. See Configuring Secure Sockets Layer Authentication for more information.

To create database links to a public target, the target Oracle Database must be accessible. Some 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.

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

To create database links to a target Oracle 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;
                

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;
/

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:

Create Database Links from Autonomous Database to an Oracle Database on a Private Endpoint

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

Note:

Database links from an Autonomous Database to a target Oracle database that is on a private endpoint are only supported in commercial regions and US Government regions.

This feature is enabled by default in all commercial regions.

This feature is enabled by default in US Government regions for newly provisioned databases.

For existing US Government databases on a private endpoint, if you want to create database links from an Autonomous Database to a target in a US Government region, you can file a Service Request at Oracle Cloud Support and request to enable the private endpoint in government regions database linking feature.

US Government regions include the following:

Depending on the type and the configuration of the target Oracle database:

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

Topics

Prerequisites for Database Links from Autonomous Database to Oracle Databases on a Private Endpoint

Lists the prerequisites to create database links from an Autonomous Database to a target Oracle database that is on a private endpoint.

To create a database link to a target Oracle database on a private endpoint:

  • The target database must be accessible from the source database's Oracle Cloud Infrastructure VCN. For example, you can connect to the target database when:

    • The target database is on a private endpoint.

    • Both the source database and the target database are in the same Oracle Cloud Infrastructure VCN.

    • The source database and the target database are in different Oracle Cloud Infrastructure VCNs that are paired.

    • The target database is an on-premises database that is connected to the source database's Oracle Cloud Infrastructure VCN using FastConnect or VPN.

  • There are two options to specify the target database, use the hostname parameter or the rac_hostnames parameter:

    • For a target on a private endpoint, DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK supports specifying a single hostname with the hostname parameter. On a private endpoint, using an IP address, SCAN IP, or a SCAN hostname is not supported (when the target is on a public endpoint, CREATE_DATABASE_LINK supports using an IP address, a SCAN IP, or a SCAN hostname).

    • When the target is an Oracle RAC database, use the rac_hostnames parameter to specify one or more hostnames with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK. This allows you to take advantage of the high availability capabilities of Oracle RAC. Using an IP address, a SCAN IP, or a SCAN hostname in the rac_hostnames value is not supported.

      When you specify a list of host names in the rac_hostnames parameter, CREATE_DATABASE_LINK uses all of the specified host names as addresses in the connect string. If one of the specified hosts is not available on the target Oracle RAC database, Autonomous Database automatically attempts to connect using another host name from the list.
  • The following ingress and egress rules must be defined for the private endpoint:

    • Define an egress rule in the source database's subnet security list or network security group such that the traffic over TCP is allowed to the target database's IP address and port number.

    • Define an ingress rule in the target database's subnet security list or network security group such that the traffic over TCP is allowed from the source database IP address to the destination port.

    See Configuring Network Access with Private Endpoints for information on configuring private endpoints with ingress and egress rules.

Note:

When your Autonomous Database instance is configured with a private endpoint, set the ROUTE_OUTBOUND_CONNECTIONS database parameter to 'PRIVATE_ENDPOINT' to specify that all outgoing database links are subject to the Autonomous Database instance private endpoint VCN's egress rules. See Enhanced Security for Outbound Connections with Private Endpoints for more information.

Create Database Links to Oracle Databases on a Private Endpoint without a Wallet

Use DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK to create database links from an Autonomous Database to a target Oracle database that is on a private endpoint and connect without a wallet (TCP).

Note:

This option is for target Oracle databases that are on a private endpoint and do not have SSL/TCPS configured.

Perform the prerequisite steps, as required. See Prerequisites for Database Links from Autonomous Database to a Target Autonomous Database on a Private Endpoint for details.

To create a database link to a target database on a private endpoint using a secure TCP connection without a wallet:

  1. On Autonomous Database 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 used within the database link, (where the target database is accessed through the VCN).

    For example:

    BEGIN
         DBMS_CLOUD.CREATE_CREDENTIAL(
             credential_name => 'PRIVATE_ENDPOINT_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.

  2. 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 => 'PRIVATE_ENDPOINT_LINK', 
             hostname => 'exampleHostname',
             port => '1522',
             service_name => 'exampleServiceName',
             ssl_server_cert_dn => NULL,
             credential_name => 'PRIVATE_ENDPOINT_CRED',
             directory_name => NULL,
             private_target => TRUE);
    END;
    /

    For a target on a private endpoint, DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK supports specifying a single hostname with the hostname parameter. On a private endpoint, using an IP address, SCAN IP, or a SCAN hostname is not supported (when the target is on a public endpoint, CREATE_DATABASE_LINK supports using an IP address, a SCAN IP, or a SCAN hostname).

    When the target is an Oracle RAC database, use the rac_hostnames parameter to specify one or more hostnames with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK. This allows you to take advantage of the high availability capabilities of Oracle RAC. Using an IP address, a SCAN IP, or a SCAN hostname in the rac_hostnames value is not supported.

    For example, with a target Oracle RAC database use the rac_hostnames parameter:

    BEGIN
         DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
             db_link_name => 'PRIVATE_ENDPOINT_LINK', 
             rac_hostnames => '["sales1-svr1.example.adb.us-ashburn-1.oraclecloud.com", 
                                "sales1-svr2.example.adb.us-ashburn-1.oraclecloud.com", 
                                "sales1-svr3.example.adb.us-ashburn-1.oraclecloud.com"]', 
             port => '1522',
             service_name => 'exampleServiceName',
             ssl_server_cert_dn => NULL,
             credential_name => 'PRIVATE_ENDPOINT_CRED',
             directory_name => NULL,
             private_target => TRUE);
    END;
    /

    DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK does not support a value of localhost for the hostname or in the rac_hostnames parameter.

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

    As shown in the example, to create a database link with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK to a target database on a private endpoint using a secure TCP connection without a wallet, all of the following are required:

    • The directory_name parameter must be NULL.

    • The ssl_server_cert_dn parameter must be NULL.

    • The private_target parameter must be TRUE.

      Note:

      If you set ROUTE_OUTBOUND_CONNECTIONS to PRIVATE_ENDPOINT, setting the private_target parameter to TRUE is not required in this API. See Enhanced Security for Outbound Connections with Private Endpoints for more information.
  3. Use the database link you created to access data in the target database.

    For example:

    SELECT * FROM employees@PRIVATE_ENDPOINT_LINK;
                  

Note:

For the credentials you create in Step 1, the Oracle 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.

See CREATE_DATABASE_LINK Procedure for additional information.

Create Database Links from Autonomous Database to Oracle Databases on a Private Endpoint with a Wallet (mTLS)

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

Note:

This option is for target Oracle databases that have SSL/TCPS configured and that are on a private endpoint.

If the target Oracle database does not have SSL/TCPS configured, you have two options:

Perform the prerequisite steps, as required. See Prerequisites for Database Links from Autonomous Database to a Target Autonomous Database on a Private Endpoint for details.

To create a database link to a target Oracle database on a private endpoint using TCP/IP with SSL (TCPS) authentication:

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

    Note:

    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.
  2. Create credentials to access your Object Store where you store the 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 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, 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 => '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 Autonomous Database 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 used within the database link, (where the target database is accessed through the VCN).

    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 => 'PEDBLINK1', 
            hostname => 'example1.adb.ap-osaka-1.oraclecloud.com',
            port => '1522',
            service_name => 'example_high.adb.oraclecloud.com',
            ssl_server_cert_dn => 'ssl_server_cert_dn',
            credential_name => 'DB_LINK_CRED',
            directory_name => 'WALLET_DIR',
            private_target => TRUE);
    END;
    /

    Note:

    If you set ROUTE_OUTBOUND_CONNECTIONS to PRIVATE_ENDPOINT, setting the private_target parameter to TRUE is not required in this API. See Enhanced Security for Outbound Connections with Private Endpoints for more information.

    For a target on a private endpoint, DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK supports specifying a single hostname with the hostname parameter. On a private endpoint, using an IP address, SCAN IP, or a SCAN hostname is not supported (when the target is on a public endpoint, CREATE_DATABASE_LINK supports using an IP address, a SCAN IP, or a SCAN hostname).

    When the target is an Oracle RAC database, use the rac_hostnames parameter to specify one or more hostnames with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK. This allows you to take advantage of the high availability capabilities of Oracle RAC. Using an IP address, a SCAN IP, or a SCAN hostname in the rac_hostnames value is not supported.

    For example, with a target Oracle RAC database use the rac_hostnames parameter:

    BEGIN
        DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
            db_link_name => 'PEDBLINK1', 
            rac_hostnames => '["sales1-svr1.example.adb.us-ashburn-1.oraclecloud.com",
                               "sales1-svr2.example.adb.us-ashburn-1.oraclecloud.com",
                               "sales1-svr3.example.adb.us-ashburn-1.oraclecloud.com"]',
            port => '1522',
            service_name => 'example_high.adb.oraclecloud.com',
            ssl_server_cert_dn => 'ssl_server_cert_dn',
            credential_name => 'DB_LINK_CRED',
            directory_name => 'WALLET_DIR',
            private_target => TRUE);
    END;
    /

    DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK does not support a value of localhost for the hostname or in the rac_hostnames parameter.

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

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

    For example:

    SELECT * FROM employees@PEDBLINK1;
                  

Note:

For the credentials you create in Step 5, the Oracle 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.

See CREATE_DATABASE_LINK Procedure for additional information.

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)

Notes for database links to other Oracle databases:

  • If you are using database links between Autonomous Database and other Oracle Databases, you might need to apply Patch 33843368 on the Oracle Database that is not an Autonomous Database. This applies to cases where the Autonomous Database instance is either the source or the target of the database link.

    See My Oracle Support Knowledge Base: Patch Requirement For Database Links Between ADB-S And Other Oracle Databases(Doc ID 2874244.1) for further details.

  • Only one wallet file is valid per directory for use with database links. You can only upload one cwallet.sso at a time to the directory you choose for wallet files (for example DBLINK_WALLET_DIR). This means with a cwallet.sso in DBLINK_WALLET_DIR you can only create database links to the databases for which the wallet in that directory is valid. To use multiple cwallet.sso files with database links you need to create additional directories and put each cwallet.sso in a different directory. When you create database links with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK, specify the directory that contains the wallet with the directory_name parameter.

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

  • Supported target Oracle database versions for database links to another Oracle Database are: 19c, 18c, 12.2.0, and 12.1.0.

  • Autonomous Database sets the SEC_CASE_SENSITIVE_LOGON parameter to true and this value cannot be changed. If your target database is not an Autonomous Database, then you must set SEC_CASE_SENSITIVE_LOGON parameter to true on the target database. If SEC_CASE_SENSITIVE_LOGON is set to false on the target database, then error ORA-28040: No matching authentication protocol is raised.

  • To list the database links, use the ALL_DB_LINKS view. See ALL_DB_LINKS for more information.

  • 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.

  • When the Autonomous Database instance is on a private endpoint, there are two options to specify the target database: use either the hostname parameter or the rac_hostnames parameter:

    • For a target on a private endpoint, DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK supports specifying a single hostname with the hostname parameter. On a private endpoint, using an IP address, SCAN IP, or a SCAN hostname is not supported (when the target is on a public endpoint, CREATE_DATABASE_LINK supports using an IP address, a SCAN IP, or a SCAN hostname).

    • When the target is an Oracle RAC database, use the rac_hostnames parameter to specify one or more hostnames with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK. This allows you to take advantage of the high availability capabilities of Oracle RAC. Using an IP address, a SCAN IP, or a SCAN hostname in the rac_hostnames value is not supported.

      When you specify a list of host names in the rac_hostnames parameter, CREATE_DATABASE_LINK uses all of the specified host names as addresses in the connect string. If one of the specified hosts is not available on the target Oracle RAC database, Autonomous Database automatically attempts to connect using another host name from the list.
    • DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK does not support a value of localhost for the hostname or in the rac_hostnames parameter.