How Does Adabas Cluster Work?

  Initial State
  Reaction to Failure

The Adabas Cluster Topology consists of
Three or more Adabas Servers configured as cluster nodes. One of these nodes takes over the role of a primary node, all others are so-called secondary nodes.
One or more Adabas Client hosts using the cluster parameter of the ADATCP protocol.
Primary Node
The Primary Node is the only component that accepts update commands. By default, the first node to be started becomes the Primary of that cluster, also called a bootstrap node. The primary node shares a Cluster Unique Identifier with all other nodes. It is possible to switch to another node (status SYNCED) as Primary Node. For more information, see CLUSTER_PRIMARY: Trigger Primary Node Switch.
Secondary Nodes
All other nodes take over the role of a Secondary Node. Write sets are devised solely from the Primary Node. A Secondary Node is only allowed to handle read commands, and update commands are rejected, returning Adabas response code 22. For more information see Cluster-Specific Adabas response and subcodes.
It is advised to have at least two secondary nodes in your cluster. For more information see Setting Up a Three-Node Cluster.