Demystifying Database Links: A Beginner's Guide to Remote Procedure Calls in Oracle

Setting Up the Database Link:

First, you need to create a database link using the CREATE DATABASE LINK statement. This link serves as a bridge between your local and the remote database. Here's an example:

CREATE DATABASE LINK my_remote_link
  CONNECT TO remote_user IDENTIFIED BY remote_password
  USING 'remote_database_host:port/service_name';

• my_remote_link: Name you choose for the database link.
• remote_user: Username for the remote database.
• remote_password: Password for the remote database user.
• remote_database_host: Hostname or IP address of the remote database server.
• port: Port number used by the remote database listener.
• service_name: Service name of the remote database.

Executing the Stored Procedure:

Once the link is established, you can directly call the remote stored procedure using its fully qualified name. Here's the syntax:

<database_link_name>.<stored_procedure_name>(<parameters>);

For example, if the stored procedure named update_customer resides on the remote database and your database link is named my_remote_link, you would call it like this:

my_remote_link.update_customer(customer_id => 123, new_name => 'foo');

Handling Parameters and Return Values:

• Parameters: You can pass parameters to the remote stored procedure just like you would with a local one. Ensure their data types and order match the remote procedure's definition.
• Return Values: If the stored procedure returns a value, you cannot directly capture it in your local code. However, you can achieve this by:
  • Modifying the remote procedure to store the return value in a table on the remote database.
  • Querying that table from your local code using the database link to retrieve the result.

Related Issues and Solutions:

• Permissions: Ensure the remote user has the necessary permissions to execute the stored procedure.
• Database Link Errors: Verify the database link details are correct (host, port, service name).
• Object Existence: Confirm the stored procedure exists on the remote database with the specified name.