This topic applies to messaging engines that are configured
to use a data store. If a messaging engine cannot connect to its data
store, for example because the database that contains the data store
is not running, it fails to start. You can tune your system to increase
the chance of a successful start of the messaging engine.
About this task
In a single-server environment, when you start the application
server the messaging engine attempts to start. If the database is
unavailable, the messaging engine might enter the stopped state and
need to be started manually.
In a high availability
environment, a messaging engine starts either as part of the server
or cluster startup, or as part of the failover process. During messaging
engine startup, the messaging engine attempts to connect to the data
store. If one of the following statements is true, the messaging engine
cannot start on the server, and the server is disabled for high availability:
- The database is unavailable or not running.
- In a failover situation, the database does not detect the loss
of the network connection to the original application server, and
therefore does not release the locks on the data store.
This disabled state can propagate to all members of the cluster.
You must manually re-enable the servers to maintain your high availability
environment.
When the
messaging engine attempts to connect to the data store, it tries to
connect for 15 minutes by default, before failing to start.
You
can increase the chance of the messaging engine starting successfully
by configuring various parameters on the database server or application
server.
Results
By configuring these parameters and custom properties, you
minimize the amount of time taken for the database server to detect
the loss of a network connection, and ensure that the messaging engine
waits for a reasonable amount of time for the database connection
to recover before attempting to start.