When the database is running, the button on the dashboard changes to Stop Database. You can perform an orderly shutdown of the cluster by clicking on the Stop Database button. When you stop the cluster, the Enterprise Manager first verifies that you indeed mean to stop the database. If you confirm the shutdown, the console stops each node in the cluster and the icons on the dashboard turn grey to indicate the database is no longer running.
You can also stop a database not currently displayed in the dashboard. Just as you can start a database from the list of databases, you can stop a running database by clicking on the database name and selecting Stop from the popup context menu.
Sometimes you don't want to completely stop the database, but do need to "pause" the database while performing administrative functions. For example, you might want to stop incoming transaction requests while you rejoin a server to a K-Safe cluster.
Click on the database name in the full list of databases on the left and select Pause from the popup menu to place the database in admin mode. While the database is paused, you can still perform all administrative actions through the Enterprise Manager, such as updating the catalog, taking snapshots, stopping and rejoining servers (when running with K-Safety), or shutting down the database.
When you are done with your administrative tasks, you can either resume the database (using the popup menu) to return to normal operation or shutdown the database as described in Section 5.2, “Stopping the Database”.
If you start a cluster with K-Safety, it is possible for individual nodes in the cluster to stop — either due to failure or by intent (when you want to perform system maintenance, for example) — without stopping the cluster as a whole. It is then possible to correct the problem with the node (such as replacing hardware) and then restart the server, bringing it back into the running cluster.
To stop an individual node manually, click on its name in the list of servers. Then click Stop on the popup menu that appears. This stops VoltDB on the node and the icon next to the server name turns gray. To restart the node and have it rejoin the cluster, simply select Rejoin or Live Rejoin from the popup menu. See Section 8.2.2, “Choosing a Rejoin Option (Live Rejoin)” for more information about the difference between live rejoin and regular, blocking rejoins.