The dmcluster service script is used to run various commands on the cluster. The script can be found in /opt/teradata/client/nn.nn/datamover/failover/, where nn.nn is the major and minor version numbers of Data Mover, for example 16.10. After the cluster configuration completes using dmcluster config.
During failover, if the active daemon, agents, Data Mover REST service, or sync service are running, the following occurs:
- The services are stopped and restarted in active mode on the primary cluster
- All standby components are stopped and the sync service on the secondary cluster is started in standby mode
- The monitoring service starts monitoring the active components by making an SSH connection to the active component servers at regular intervals to check if the services are up and running
- A failover sequence is initiated
- The failover sequence shuts down the daemon, Data Mover REST, agents, ActiveMQ, and sync service on the active servers and starts the daemon, Data Mover REST, agents, ActiveMQ, and sync service in active mode on the standby server
- An attempt is made to the start the old active sync service in standby mode
Once the failover sequence completes, the monitoring service shifts to the standby monitoring server and begins monitoring the new active components. If the monitoring service finds a running Data Mover REST, daemon, DSC, or ActiveMQ process on the standby server, it automatically shuts it down to prevent two services from being active at the same time.
Running the dmcluster status command at this point displays the following:
ERROR: The following error may indicate incorrect configuration of high availability in Data Mover. Check the Data Mover Customer Installation guide for high availability setup Cause: java.lang.Exception: The following properties are incorrect: The hostname/IP address for local daemon is set to localhost in the properties file The hostname/IP address for remote daemon is set to localhost in the properties file The hostname/IP address for local monitor is set to localhost in the properties file The hostname/IP address for remote monitor is set to localhost in the properties file The hostname/IP address for local repository is set to localhost in the properties file The hostname/IP address for remote repository is set to localhost in the properties file The hostname/IP address for local agent is set to localhost in the properties file The hostname/IP address for remote agent is set to localhost in the properties file Error running status
The dmFailover.log provides more information on the failover sequence.
Refer the Teradata® Data Mover Installation, Configuration, and Upgrade Guide for Customers, B035-4102 to know more about how to configure a failover. This section talks about all the components used in a failover.