Executive summary
DB2 High Availability Disaster Recovery (HADR) is an easy to use data replication feature that provides a high availability (HA) solution for both partial and complete site failures.
However, given the wide variety of users’ requirements, there is no one ideal configuration for HADR. The decisions you make in setting up, tuning, and maintaining your HADR environment are often the result of weighing various pros and cons. For instance, you might need to balance the competing requirements of the availability of your database with protection from data loss. The good news is that this need to find a balance does not necessarily imply that one requirement needs to suffer.
This document provides a number of recommendations for setting up and maintaining your HADR environment in ways that help balance the protection HADR provides with performance and cost. The following specific areas of focus are covered:
- Setting up your system for fast failovers
- Tuning parameters to improve network performance
- Tuning parameters to minimize the impact of HADR-related logging on performance
- Choosing the right table reorganization method and load operation in an HADR environment
Introduction to HADR
HADR replicates data changes from a source database (called the primary) to a target database (called the standby). Each database uses its own storage, as this is a shared-nothing architecture. HADR provides fast failover in case the primary database fails. You can also switch the roles of primary and standby databases easily and quickly for scenarios such as rolling upgrade or rolling maintenance, keeping down time to minimum. HADR is versatile and is fully integrated into DB2 database systems requiring no special hardware or software and using a standard TCP interface to connect the primary and standby databases. Setup requires only a few database configuration parameters.
A central tenet of HADR is that the performance and availability of the database should not be impacted by challenges such as sudden spikes in the workload (which impacts the amount of log replay activity on the standby) or failed servers or networks (which can lead to a failover).
Tuning your HADR solution for optimal performance should follow some basic tenets up front to avoid potential issues over time. As well, an HADR setup has a number of implications for your database maintenance activities that you should know. This best practice paper addresses these points. It focuses on providing guidelines and specific recommendations for designing your HADR infrastructure and configuring your database in order to improve HADR-related performance, specifically logging and failover speed.
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