The following figure illustrates the architecture of a database with four active nodes in a management domain.
The figure illustrates a management domain that consists of a database and four HADB node processes in the database. These node processes are indicated by n0, n1, n2, and n3. Host A and Host B represent the cluster nodes and form the Data Redundancy Units, or DRUs (Host A:DRU0 and Host B:DRU1) for HADB.
Management agent MA1 manages n0 and n2, and management agent MA2 manages n1 and n3. The management agent is responsible for monitoring the health of the node and restarting the node when necessary. The management agent also handles the management operations requests from the clients.
If the management agent fails on the cluster node, the agent must be restarted on the same node so that the agent can continue to monitor the HADB nodes and to provide management operations. Therefore, the management agent must be made highly available.