In today's digital landscape, businesses rely heavily on their data infrastructure for continuous operations. Any disruption in database availability can lead to significant financial losses and reputational damage. To address this concern, IBM offers a robust solution called High Availability Disaster Recovery (HADR) in their DB2 database management system. HADR ensures continuous availability, data integrity, and seamless failover between primary and standby databases. This article will provide a detailed explanation of IBM DB2 HADR, including its mechanism and implementation steps.

Understanding IBM DB2 HADR

HADR is a database replication feature provided by IBM DB2 that enables continuous availability of critical data and rapid disaster recovery. It establishes a synchronous or asynchronous replication mechanism between a primary and a standby database. The primary database handles read and write operations while actively replicating the log records to the standby database. In the event of a primary database failure, the standby database takes over seamlessly, minimizing downtime and data loss.

How Does It Work ?

HADR works by maintaining a synchronized copy of the primary database on a standby server. The primary server logs all changes made to the database and sends these log records to the standby server in real-time. The standby server applies the log records to its copy of the database, keeping it up to date with the primary. In the event of a failure or planned outage on the primary server, HADR enables automatic failover to the standby server, minimizing downtime and data loss. Manual failover can also be performed when necessary. With its continuous log shipping and failover capabilities, IBM DB2 HADR ensures high availability and effective disaster recovery for DB2 databases.

Implementation

Implementing IBM DB2 HADR involves a series of configuration and setup steps on both the primary and standby servers. Let's go through these steps in detail:

Enable Log Archiving:
To ensure proper log retention, enable log archiving on the primary server using the following command:

Take an Offline Backup (Optional):
Perform an offline backup of the database on the primary server. Although not mandatory for HADR setup, it is recommended for initial synchronization and as a fallback option.

Configure HADR Parameters on the Primary Database:
Update the HADR configuration parameters on the primary database using the following commands:

Take an Offline Backup for HADR Configuration:
Perform another offline backup of the database, which will be used for setting up HADR.

In case of problem of backup, apply the following steps

Verify db2level on Server 1

Copy Backup to Standby Server: 
Copy the database backup from the primary server to the standby server.

Specify HADR Ports for Both Servers: 
Apply the following commands on both servers to specify HADR ports:

Update /etc/services File: 

Add the following lines to the /etc/services file on both servers:

Start HADR on Both Servers: 
Start HADR on the standby server first, followed by the primary server, using the following commands:

Verify HADR Configuration: 
Verify the HADR configuration on both servers using the following command:

Testing HADR Functionality: 
After completing the HADR setup, it is essential to test its functionality.
The following steps outline a simple test scenario:

To Remember

IBM DB2 HADR provides an effective solution for achieving high availability and disaster recovery in database systems. By establishing a synchronous or asynchronous replication mechanism between primary and standby databases, businesses can minimize downtime and data loss during critical events. The implementation steps outlined in this article guide users through the configuration process, ensuring a reliable and resilient database infrastructure. With IBM DB2 HADR, organizations can confidently maintain continuous operations and protect their valuable data.

Author : Youssef Sbai Idrissi
https://www.linkedin.com/in/sbaiidrissiyoussef/