Administration Guide

Appendix O. Configuring Multiple Logical Nodes

Typically, you configure DB2 Enterprise - Extended Edition to have one database partition server assigned to each machine. There are several situations, however, in which it would be advantageous to have several database partition servers running on the same machine. This means that the configuration can contain more nodes than machines. In these cases, the machine is said to be running multiple logical nodes if they participate in the same instance. If they participate in different instances, this machine is not tuning multiple logical nodes.

With multiple logical node support, you can choose from three types of configurations:

• A standard configuration, where each machine has only one database partition server.
• A multiple logical node configuration, where a machine has more than one database partition server.
• A configuration where several logical nodes run on each of several machines.

Configurations that use multiple logical nodes are useful when the system runs queries on a machine that has symmetric multiprocessor (SMP) architecture. The ability to configure multiple logical nodes on a machine is also useful if a machine fails. If a machine fails (causing the database partition server or servers on it to fail), you can restart the database partition server (or servers) on another machine using the DB2START NODENUM command. This ensures that user data remains available.

Another benefit is that multiple logical nodes can exploit SMP hardware configurations. In addition, because database partitions are smaller, you can obtain better performance when performing such tasks as backing up and restoring database partitions and table spaces, and creating indexes.

You can configure multiple logical nodes in one of two ways:

• Configure the logical nodes (database partitions) in the db2nodes.cfg file. You can then start all the logical and remote nodes with the DB2START command or its associated API.

  Note:

  For Windows NT, you must use db2ncrt to add a node if there is no database in the system; or, DB2START ADDNODE command if there is one or more databases. Within Windows NT, the db2nodes.cfg file should never be manually edited.

• Restart a logical node on another processor on which other logical database partitions (nodes) are already running. This allows you to override the hostname and port number specified for the logical database partition in db2nodes.cfg.

To configure a logical database partition (node) in db2nodes.cfg, you must make an entry in the file to allocate a logical port number for the node. Following is the syntax you should use:

   nodenumber hostname logical-port netname

   nodenumber hostname computername logical_port netname