Global Data Services (GDS) is a feature provided by Oracle for managing and optimizing database workloads in a distributed and global environment. It is designed to help organizations ensure high availability, scalability, and performance for their Oracle databases across multiple geographic regions. Here are some key aspects of Oracle Global Data Services:

1. Global Workload Management: GDS allows organizations to distribute database workloads across multiple database instances located in different geographic regions. This helps in load balancing and ensures that users and applications are directed to the most appropriate database instance for their needs.
2. High Availability: GDS enhances database availability by providing failover capabilities. If one database instance becomes unavailable, GDS can automatically redirect traffic to a standby instance, minimizing downtime.
3. Latency-Based Routing: GDS can route database requests based on latency considerations. It can direct traffic to the database instance that provides the lowest latency for a given user or application, optimizing performance.
4. Active-Active Configurations: GDS supports active-active database configurations where multiple database instances can serve read and write requests simultaneously. This can improve both performance and availability.
5. Geographic Distribution: GDS allows organizations to deploy database instances in multiple data centers or cloud regions across the world, making it suitable for global enterprises with a distributed user base.
6. Integration with Oracle Database: GDS is designed to work with Oracle Database and is typically used in conjunction with Oracle Real Application Clusters (RAC) and Oracle Data Guard for high availability and data protection.
7. Management and Monitoring: Oracle provides tools and utilities for configuring, managing, and monitoring GDS configurations. This includes the Global Data Services Control (GDSCTL) utility.
8. Load Balancing and Failover Policies: Administrators can define load balancing and failover policies to determine how GDS routes traffic and responds to database instance failures.
9. Traffic Directories: GDS uses traffic directors to manage routing policies. These traffic directors are responsible for directing database connections to the appropriate database instances based on the defined policies.
10. Global Service Names: GDS uses global service names to abstract the underlying database instances. Users and applications connect to these global service names, and GDS handles the routing to the specific database instances.

Here’s a step-by-step tutorial on setting up and using Oracle GDS:

Prerequisites:

• Oracle Database instances (RAC or standalone) installed and configured.
• Basic understanding of Oracle Database concepts.

Step 1: Install Oracle Database Software: Ensure that Oracle Database software is installed and configured on the servers where you plan to create database instances.

Step 2: Prepare the Environment:

• Set up a network infrastructure with connectivity between the database servers.
• Ensure that your TNS (Transparent Network Substrate) configuration is correctly set up.

Step 3: Enable GDS in Database:

• Log in to your database server as a DBA user.
• Open SQL*Plus or any other SQL client.
• Connect to the database instance you want to configure for GDS.
• Enable GDS by setting the global_names parameter to TRUE in the initialization parameter file (init.ora or spfile.ora).
  ALTER SYSTEM SET global_names=TRUE SCOPE=SPFILE;
• Restart the database instance for the changes to take effect.
  
  Step 4: Configure Global Service:
  • Create a Global Service Name (GSN) to represent your database. GSNs are used to abstract the underlying database instances.
    
    CREATE GLOBAL SERVICE my_global_service
SET current_instance = 'INSTANCE_NAME'
USING '(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=HOSTNAME)(PORT=PORT)))';
    
    Replace my_global_service with your desired service name, INSTANCE_NAME with the name of your database instance, HOSTNAME with the hostname of the database server, and PORT with the database listener port.
• Repeat the above step for each database instance you want to include in the GDS configuration.

Step 5: Configure GDS Director:

Create a GDS director to manage routing policies.

BEGIN
  DBMS_GDS.CREATE_SERVICE_DIRECTOR(
    director_name => 'my_director',
    affinity_level => 'NONE',
    global_service_names => 'my_global_service'
  );
END;
/

Replace my_director with your preferred director name.
Add more GSNs or modify existing ones to include additional database instances if necessary.

Step 6: Define Policies:

Define your routing policies. GDS supports different policies, such as latency-based, load-based, and failover-based policies.

BEGIN
  DBMS_GDS.ADD_POLICY(
    director_name => 'my_director',
    global_service_name => 'my_global_service',
    goal => 'LATENCY',
    metric => 'SERVICE_TIME',
    affinity_level => 'SERVICE',
    threshold => 20
  );
END;
/

In this example, a latency-based policy is created based on service time with a threshold of 20 milliseconds. Adjust the parameters according to your requirements.

Step 7: Test and Monitor:

Test your GDS configuration by connecting to the GSNs you’ve created. You can use the GDS service name to connect:

sqlplus username/password@my_global_service

2. Monitor GDS using Oracle Enterprise Manager or other monitoring tools to ensure that the routing policies are working as expected.

Step 8: Expand and Optimize: As your requirements change, you can modify your GDS configuration, add more database instances, and adjust policies to optimize performance and availability.

This tutorial provides a basic overview of setting up Oracle Global Data Services. The actual configuration can vary depending on your specific requirements and network architecture. Be sure to refer to Oracle’s official documentation for detailed instructions and best practices: https://docs.oracle.com/en/database/oracle/oracle-database/19/dgbps/index.html