Topology Glossary

This glossary provides definitions related to topology and topology changes.

Instance topology
The members that are part of a Db2® instance. For a Db2 pureScale® environment, the topology consists of members that are listed in the configuration file db2nodes.cfg. The topology of a non-pureScale environment consists of a single member number, which is the partition number from the db2nodes.cfg. If a db2nodes.cfg does not exist then member number 0 is used.
Database topology

The instance topology reflected to the database. Instance and database topology can differ, see topology change.

Topology change

A topology change occurs when an operation updates and causes a difference in the instance topology and the database topology. This can be through adding or dropping of members through db2iupdt command, restore and rollforward, or moving a database to another instance using a physical copy or a snapshot. A topology change can be explicit or implicit.

Explicit topology change
An explicit topology change is when a member is added or dropped through the db2iupdt command.
Implicit topology change
An implicit topology change is when the difference in the instance topology and database topology is caused by operations other than through the db2iupdt command. This can be through operations such as restore or rollforward, or from moving a database from one instance to another instance with a different instance topology through physical copy or snapshot.
Mixed topology
The terminology used to describe a Db2® pureScale® HADR environment where the primary and standby clusters have different instance topologies, different database topologies, or both. For example, an environment where the primary has three members and the standby has one member.
Member reconciliation
The process of adding a member to, or dropping a member from, the database topology. This definition applies when a member has first been added to, or removed from, the instance topology, or after changing from a Db2 pureScale to a non-Db2 pureScale instance. This process can also involve adding or removing database meta files and log files for the member, as well as writing a log record to record the topology change event.
Source topology
The database topology of a backup image when the backup is taken, or the database topology when a physical copy or snapshot is taken.
Target topology
The instance topology where a backup, a snapshot, or a physical copy is restored into.