Introduction to the DB2 High Availability feature
In today's fast-paced world, time is money. More importantly, downtime equals money lost. This is why high availability is so important for all businesses, large and small. A highly available database solution ensures that, should any integral part of your database solution go down, your system would seamlessly fail over to a backup. However, without a cluster manager, this "failover" is not automatic. A database administrator must be paged, and must physically go to the database server and manually issue a takeover command. This is where the power of the integrated HA solution comes into play.
The integrated HA solution, called the DB2 High Availability feature, was introduced in DB2 9.5. In this solution, a cluster manager, Tivoli Systems Automation / Reliable Scalable Cluster Technology (TSA/RSCT), comes bundled with DB2 for Linux, UNIX, and Windows Workgroup Edition and Enterprise Edition. It is responsible for monitoring integral database resources and, in the event of a failure, taking the appropriate action. The main advantages of the integrated solution are:
- It is simple: The DBA does not need to learn a new set of cluster manager commands to manage resources.
- It is integrated: Using the db2haicu tool, DB2 seamlessly interacts with TSA, triggering the correct actions. DB2 comes with TSA/RSCT bundled. As you apply DB2 fix packs, the fix packs automatically upgrade your TSA/RSCT level to pick up critical TSA/RSCT fixes, if necessary.
In a typical integrated HA solution configuration, TSA/RSCT is installed on both hosts. It is responsible for monitoring entities such as network interfaces, DB2 instances, and HADR databases. The client connects to the primary database using the public network using a virtual IP address. In the event of a failure on the primary host, this virtual IP address fails over to the standby. From the perspective of the client, there is no down time, as the transition is automatic. If there are two network interfaces on each host, a private network can be set up exclusively for HADR replication.
Figure 1. Integrated HA solution
The integrated HA solution using TSA/RSCT as the cluster manager is available for use on Linux and AIX in DB2 9.5 for Linux, UNIX, and Windows and later, and on Solaris in V9.7 and later.