CREATE_DATABASE_LINK Procedure

This procedure creates a database link to a target database in the schema calling the API.

The overloaded forms support the following:

When you use the gateway_params parameter, this enables you to create a database link with Oracle-managed heterogeneous connectivity where the link is to a supported non-Oracle database.
When you use the rac_hostnames parameter, this enables you to create a database link from an Autonomous Database on a private endpoint to a target Oracle RAC database. In this case, you use the rac_hostnames parameter to specify the host names of one or more individual nodes of the target Oracle RAC database.

Syntax

DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
       db_link_name         IN VARCHAR2,
       hostname             IN VARCHAR2,
       port                 IN NUMBER,
       service_name         IN VARCHAR2,
       ssl_server_cert_dn   IN VARCHAR2 DEFAULT,
       credential_name      IN VARCHAR2 DEFAULT,
       directory_name       IN VARCHAR2 DEFAULT,
       gateway_link         IN BOOLEAN DEFAULT,
       public_link          IN BOOLEAN DEFAULT,
       private_target       IN BOOLEAN DEFAULT
       gateway_params       IN CLOB DEFAULT);

DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
       db_link_name         IN VARCHAR2,
       rac_hostnames        IN CLOB,
       port                 IN NUMBER,
       service_name         IN VARCHAR2,
       ssl_server_cert_dn   IN VARCHAR2 DEFAULT,
       credential_name      IN VARCHAR2 DEFAULT,
       directory_name       IN VARCHAR2 DEFAULT,
       gateway_link         IN BOOLEAN DEFAULT,
       public_link          IN BOOLEAN DEFAULT,
       private_target       IN BOOLEAN DEFAULT);

Parameters

Parameter	Description
`db_link_name`	The name of the database link to create.
`hostname`	The hostname for the target database. Specifying `localhost` for `hostname` as is not allowed. When you specify a connection with Oracle-managed heterogeneous connectivity by supplying the `gateway_params` parameter, note the following: When the `db_type` value is `google_bigquery` the `hostname` is not used and you can provide value such as `example.com`. When the `db_type` value is `snowflake` the `hostname` is the Snowflake account identifier. To find your Snowflake account identifier, see Account Identifier Formats by Cloud Platform and Region. Use this parameter or `rac_hostnames`, do not use both. The `DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK` input should mention the scan name of the target Dedicated Autonomous Database as the 'hostname' parameter.
`rac_hostnames`	Specifies hostnames for the target Oracle RAC database. The value is a JSON array that specifies one or more individual host names for the nodes of the target Oracle RAC database. Multiple host names can be passed in JSON, separated by a "`,`". For example: `'["sales1-svr1.domain", "sales1-svr2.domain", "sales1-svr3.domain"]'` 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. Use this parameter or `hostname`, do not use both. Specifying `localhost` for a `rac_hostname` value is not allowed.
`port`	Specifies the port for the connections to the target database. When you specify a connection with Oracle-managed heterogeneous connectivity using the `gateway_params` parameter, set the port based on the `db_type` value: `awsredshift`: use port `5439` `azure`: use port `1433` `db2`: use port `2500` for Db2 versions >= 11.5.6 `db2`: use port `5000` for Db2 versions <= 11.5.5 `google_analytics`: use port `443` `google_bigquery`: use port `443` `hive`: use port `433` `mongodb`: use port `27017` `mysql`: use port `3306` `mysql_community`: use port `3306` `postgres`: use port `5432` `salesforce`: use port `19937` `servicenow`: use port `443` `snowflake`: use port `443`
`service_name`	The `service_name` for the database to link to. For a target Autonomous Database, find the service name by one of the following methods: Look in the `tnsnames.ora` file in the `wallet.zip` that you download from an Autonomous Database for your connection. Click Database connection on the Oracle Cloud Infrastructure Console. Each connection string listed in the Connection string column includes a `service_name` entry with the connection string for the corresponding service. See View Connection Strings for an Autonomous Database for more information. Query `V$SERVICES` view. For example: `SELECT name FROM V$SERVICES;` When you specify a connection with Oracle-managed heterogeneous connectivity using the `gateway_params` parameter, the `service_name` is the database name of the non-Oracle database.
`ssl_server_cert_dn`	The DN value found in the server certificate. Oracle-managed heterogeneous connectivity is preconfigured with a wallet that contains most of the common trusted root and intermediate SSL certificates. The `ssl_server_cert_dn` must be `NULL` when you supply the `gateway_params` parameter or do not include the `ssl_server_cert_dn` parameter (the default value is `NULL`). Public Endpoint Link to an Autonomous Database Target without a Wallet: To connect to an Autonomous Database target on a public endpoint without a wallet (TLS): The `directory_name` parameter must be `NULL`. The `ssl_server_cert_dn` parameter must be `NULL` or do not include this parameter (the default value is `NULL`). Private Endpoint Link without a Wallet: To connect to an Oracle Database on a private endpoint without a wallet: The target database must be on a private endpoint. The `directory_name` parameter must be `NULL`. The `ssl_server_cert_dn` parameter must be `NULL` or do not include this parameter (the default is `NULL`). The `private_target` parameter must be `TRUE`.
`credential_name`	The name of a stored credential created with `DBMS_CLOUD.CREATE_CREDENTIAL`. This is the credentials to access the target database.
`directory_name`	The directory for the `cwallet.sso` file. The default value for this parameter is `'data_pump_dir'.` Oracle-managed heterogeneous connectivity is preconfigured with a wallet that contains most of the common trusted root and intermediate SSL certificates. The `directory_name` parameter is not required when you supply the `gateway_params` parameter. Public Endpoint Link to an Autonomous Database Target without a Wallet: To connect to an Autonomous Database on a public endpoint without a wallet (TLS): The `directory_name` parameter must be `NULL`. The `ssl_server_cert_dn` parameter must be `NULL` or do not include this parameter (the default value is `NULL`). In addition, to connect to an Autonomous Database with TCP, the `ssl_server_cert_dn` parameter must be `NULL` or do not include this parameter (the default value is `NULL`). Private Endpoint Link without a Wallet: To connect to a target Oracle Database on a private endpoint without a wallet: The target database must be on a private endpoint. The `directory_name` parameter must be `NULL`. The `ssl_server_cert_dn` parameter must be `NULL` or do not include this parameter (the default value is `NULL`). The `private_target` parameter must be `TRUE`.
`gateway_link`	Indicates if the database link is created to another Oracle Database or to an Oracle Database Gateway. If `gateway_link` is set to `FALSE`, this specifies a database link to another Autonomous Database or to another Oracle Database. If `gateway_link` is set to `TRUE`, this specifies a database link to a non-Oracle system. This creates a connect descriptor in the database link definition that specifies `(HS=OK)`. When `gateway_link` is set to `TRUE` and `gateway_params` is `NULL`, this specifies a database link to a customer-managed Oracle gateway. The default value for this parameter is `FALSE`.
`public_link`	Indicates if the database link is created as a public database link. To run `DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK` with this parameter set to `TRUE`, the user invoking the procedure must have `EXECUTE` privilege on the credential associated with the public database link and must have the `CREATE PUBLIC DATABASE LINK` system privilege. The `EXECUTE` privilege on the credential can be granted either by the `ADMIN` user or by the credential owner. The default value for this parameter is `FALSE`.
`private_target`	When a database link accesses a hostname that needs to be resolved in a VCN DNS server, specify the `private_target` parameter with value `TRUE`. When `private_target` is `TRUE`, the `hostname` parameter must be a single hostname (on a private endpoint, using an IP address, a SCAN IP, or a SCAN hostname is not supported). The default value for this parameter is `FALSE`.
`gateway_params`	`db_type` This parameter specifies the target database type for Oracle-managed heterogeneous connectivity to connect to non-Oracle databases. The `db_type` value is one of: `awsredshift` `azure` `db2` `google_analytics` `google_bigquery` * See Usage Notes for additional supported `gateway_params` when `db_type` is `google_bigquery`. `hive` * See Usage Notes for additional supported `gateway_params` when `db_type` is `hive`. `mongodb` `mysql` `postgres` `salesforce` * See Usage Notes for additional supported `gateway_params` when `db_type` is `salesforce`. `servicenow` * See Usage Notes for additional supported `gateway_params` when `db_type` is `servicenow`. `snowflake` * See Usage Notes for additional supported `gateway_params` when `db_type` is `snowflake`. `NULL` When `gateway_params` is `NULL` and `gateway_link` is set to `TRUE`, this specifies a database link to a customer-managed Oracle gateway. Specify the parameter with the `json_object` form. For example: `gateway_params => json_object('db_type' value 'awsredshift')` When `gateway_params` is `NULL` and `private_target` is `TRUE`, if `directory_name` is `NULL`, a TCP-based database link is created. When `gateway_params` is `NULL` and `private_target` is `TRUE`, if `directory_name` is `NULL`, a TCPS-based database link is created.

Usage Notes

When you specify the gateway_params parameter, for some db_type values, additional gateway_params parameters are supported:

`db_type`	Additional `gateway_params` Values
`google_analytics`	When the `db_type` is `google_analytics`, the credential you specify must be a Google OAuth credential (`gcp_oauth2)` See CREATE_CREDENTIAL Procedure for more information.
`google_bigquery`	When the `db_type` is `google_bigquery`, the credential you specify must be a Google OAuth credential (`gcp_oauth2)` See CREATE_CREDENTIAL Procedure for more information. When `db_type` is `google_bigquery`, the parameter `project` is valid. This parameter specifies the project name for `google_bigquery` and is required. The table name you specify when you use `SELECT` with Google BigQuery must be in quotes. For example: `SELECT * FROM "sales"@GOOGLE_BIGQUERY_LINK`
`hive`	When `db_type` is `hive`, the parameter `http_path` is valid. This parameter specifies the HttpPath value, if required, to connect to the Hive instance.
`salesforce`	When the `db_type` is `salesforce`, the parameter: `security_token` is valid. A security token is a case-sensitive alphanumeric code. Supplying a `security_token` value is required to access Salesforce. For example: `gateway_params => JSON_OBJECT( 'db_type' value 'salesforce', 'security_token' value 'security_token_value' )` See Reset Your Security Token for more information.
`servicenow`	To connect to ServiceNow and get data you must supply the gateway parameters `directory_name` and `file_name`. These parameters specify a model file (REST config file) that maps the JSON response to the relational model. The model file specifies the endpoints, table mapping, and HTTP response code for processing the JSON response. See Model file syntax and Example Model file for more information. When you use `gateway_params` parameter with `db_type` `servicenow`, there are two supported options: Basic Authentication: you must supply the `gateway_params` parameter `db_type` with the value `'servicenow'`, and supply the `directory_name` and `file_name` parameters along with username/password type credentials. OAuth 2.0 Authentication: you must supply the `gateway_params` parameter `db_type` with the value `'servicenow'`, and the `directory_name`, `file_name`, and `token_uri` parameters, along with OAuth type credentials. The `directory_name` parameter specifies the directory with the ServiceNow REST config file. You could create this directory as follows: `create or replace directory servicenow_dir as 'SERVICENOW_DIR';` Obtain and download the ServiceNow REST config file to the specified directory. For example: `exec DBMS_CLOUD.get_object('servicenow_dir_cred', 'https://objectstorage.<...>/servicenow.rest','SERVICENOW_DIR');` Set the `file_name` value to the name of the REST config file you downloaded, "`servicenow.rest`". Then you can use the ServiceNow REST config file with either basic authentication or OAuth2.0.
`snowflake`	When the `db_type` is `SNOWFLAKE`, the optional parameters: `role`, `schema`, and `warehouse` are valid. These values specify a different schema, role, or warehouse value, other than the default. For example: `gateway_params => JSON_OBJECT( 'db_type' value 'snowflake', 'role' value 'ADMIN', 'schema' value 'PUBLIC', 'warehouse' value 'TEST' )`

When you use the private_target parameter, note that database links from an Autonomous Database to a database service 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, please 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:
- Oracle Cloud Infrastructure US Government Cloud with FedRAMP Authorization
- Oracle Cloud Infrastructure US Federal Cloud with DISA Impact Level 5 Authorization
When connecting to a non-Oracle database, database linking is only supported if the target database is accessible through a public IP or a public hostname.
To run DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK with a user other than ADMIN, you need to grant EXECUTE and CREATE DATABASE LINK privileges to that user. For example, run the following command as ADMIN to grant privileges to atpc_user:
```
GRANT EXECUTE ON DBMS_CLOUD_ADMIN TO atpc_user;
GRANT CREATE DATABASE LINK TO atpc_user;
```
In addition, when you create a Database Link in a schema other than the ADMIN schema, for example in a schema named atpc_user, the atpc_user schema must own the credential you use with DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK.
Only one wallet file is valid per directory specified with the directory_name parameter. You can only upload one cwallet.sso at a time to the directory you choose for wallet files. This means with a cwallet.sso in a directory, 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.

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

To create a database link to an Autonomous Database, set GLOBAL_NAMES to FALSE on the source database (non-Autonomous Database).

SQL> ALTER SYSTEM SET GLOBAL_NAMES = FALSE;
 
System altered.

SQL> SHOW PARAMETER GLOBAL_NAMES
NAME                     TYPE        VALUE
----------------------   ----------- -----------
global_names             boolean     FALSE

When the private_target parameter is TRUE, the hostname parameter specifies a private host inside the VCN.

Examples

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

BEGIN
  DBMS_CLOUD.CREATE_CREDENTIAL(
    credential_name => 'AWS_REDSHIFT_LINK_CRED',
    username => 'NICK',
    password => 'password'
  );
DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
          db_link_name => 'AWSREDSHIFT_LINK', 
          hostname => 'example.com', 
          port => '5439',
          service_name => 'example_service_name',
          ssl_server_cert_dn => NULL,
          credential_name => 'AWS_REDSHIFT_LINK_CRED',
          gateway_params => JSON_OBJECT('db_type'  value 'awsredshift'));
END;
/

BEGIN
  DBMS_CLOUD.CREATE_CREDENTIAL(
    credential_name => 'PRIVATE_ENDPOINT_CRED',
    username => 'db_user',
    password => 'password'
  );
DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
          db_link_name => 'PRIVATE_ENDPOINT_DB_LINK', 
          hostname => 'exampleHostname', 
          port => '1521',
          service_name => 'exampleServiceName',
          credential_name => 'PRIVATE_ENDPOINT_CRED',
          ssl_server_cert_dn => NULL,
          directory_name => NULL,
          private_target => TRUE);
END;
/

BEGIN
  DBMS_CLOUD.CREATE_CREDENTIAL(
    credential_name => 'GOOGLE_BIGQUERY_CRED',
    params => JSON_OBJECT( 'gcp_oauth2' value JSON_OBJECT(
          'client_id' value 'client_id',
          'client_secret' value 'client_secret', 
          'refresh_token' value 'refresh_token' )));

DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
          db_link_name => 'GOOGLE_BIGQUERY_LINK', 
          hostname => 'example.com', 
          port => '443',
          service_name => 'example_service_name',
          credential_name => 'GOOGLE_BIGQUERY_CRED',
          gateway_params => JSON_OBJECT(
                     'db_type' value 'google_bigquery',
                     'project' value 'project_name1' ));
END;
/

The table name you specify when you use SELECT with Google BigQuery or Google Analytics must be in quotes. For example:

SELECT * FROM "sales"@GOOGLE_BIGQUERY_LINK

Use the rac_hostnames parameter with a target Oracle RAC database on a private endpoint.

BEGIN
  DBMS_CLOUD.CREATE_CREDENTIAL(
     credential_name => 'DB_LINK_CRED1',
     username => 'adb_user',
     password => 'password');
      DBMS_CLOUD_ADMIN.CREATE_DATABASE_LINK(
     db_link_name => 'SALESLINK', 
     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 => 'CN=adb.example.oraclecloud.com,OU=Oracle BMCS FRANKFURT,O=Oracle Corporation,L=Redwood City,ST=California,C=US',
     credential_name => 'DB_LINK_CRED1',
     directory_name => 'EXAMPLE_WALLET_DIR',
     private_target => TRUE);
END;
/

Parent topic: Summary of DBMS_CLOUD_ADMIN Subprograms

Oracle Cloud Infrastructure Documentation