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

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

Depending on the type and the configuration of the target Oracle AI Database:

Another Oracle AI Database, such as on-premises or a Database Cloud Service database, on a private endpoint that is configured for SSL (TCPS): In this case you can create the database link with a wallet, and the database link communicates with TCPS. See Create Database Links from Autonomous AI Database to Oracle AI Databases on a Private Endpoint with a Wallet (mTLS) for details:
Oracle AI Database, such as on-premises or a Database Cloud Service database, on a private endpoint that is configured for TCP: In this case you create the database link without a wallet and the database link communicates with TCP. See Create Database Links to Oracle AI Databases on a Private Endpoint without a Wallet for details

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

Prerequisites

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

To create a database link to a target Oracle AI 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 AI 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 Configure Network Access with Private Endpoints for information on configuring private endpoints with ingress and egress rules.

Note: When your Autonomous AI Database instance is configured with a private endpoint, set the ROUTE_OUTBOUND_CONNECTIONS database property to specify that all outgoing database links are subject to the Autonomous AI 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 AI Databases on a Private Endpoint without a Wallet

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

Note: This option is for target Oracle AI 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 AI Database to Oracle AI Databases 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:

On Autonomous AI 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.
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 the ROUTE_OUTBOUND_CONNECTIONS database property, 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.
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 AI 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 AI Database to Oracle AI Databases on a Private Endpoint with a Wallet (mTLS)

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

Note: This option is for target Oracle AI Databases that have SSL/TCPS configured and that are on a private endpoint.

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

You can configure the target Oracle AI Database to use TCP/IP with SSL (TCPS) authentication. See Configuring Transport Layer Security Authentication for information on configuring SSL/TCPS.
You can connect to the target Oracle AI Database with TCP. See Create Database Links to Oracle AI Databases on a Private Endpoint without a Wallet for details.

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

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

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 AI Database. Store wallet files in a secure location. Share wallet files only with authorized users.
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.
Create a directory on Autonomous AI Database for the wallet file cwallet.sso.

For example:
```
 CREATE DIRECTORY WALLET_DIR AS 'directory_path_of_your_choice';
```
See Create Directory in Autonomous AI 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, 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.
On Autonomous AI 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.
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 the ROUTE_OUTBOUND_CONNECTIONS database property, 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.
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 AI 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.