You can configure the system so that, if there is a problem
with a dependent external system resource, the enterprise application can continue.
Before you begin
During the time that the system resource is unavailable, there
must be no exceptions in the enterprise application, or messages on the exception destination
that must be resolved later.
About this task
Add a maintenance level to an external system resource
that is used by the deployed message-driven bean (MDB) of one of the
enterprise applications.
The act of applying the maintenance level requires the system resource
(for example, a database) to be unavailable for about five minutes.
The
JCA MBean emits JMX notifications to indicate that the MDB is paused, and that the
MDB has resumed. Consider
registering a message listener on the JCA MBean to receive the JMX
notifications.
Procedure
- Navigate to the deployed enterprise application that contains
the MDB.
- From the MDB,
navigate to its JMS activation specification. Click and
click Pause on the administrative panel for
the MDB.
- When you receive a JMX notification and a log entry indicating
that the MDB is paused,
stop the database and apply the maintenance level. While
the MDB is paused,
no messages are sent to the exception destination and no error messages
appear in the console related to the stopped database.
- Restart the database and test that it is working as expected.
- Log on to the administrative console again, navigate to
the same enterprise application
and click Resume on the administrative panel
for the MDB. You can
also resume the MDB by
using scripting and the JCA MBean. The initial JMX notification and
log entry indicate which MBean to use to resume the MDB. The
MDB begins to be driven
with the messages that are on the destination.
Results
You have paused and resumed an application while an external
resource that it uses is not available for a short time.