121.What is the use of “Destination” in JMS? How many types of “Destinations” are available in JMS?

• A destination is a lightweight object that is stored in JNDI.
• It is the target on a JMS server for sending or receiving messages.
• The JMS destination types are:
• Queue
• Topic

122.Explain about “Queue Destinations”?
In JMS point-to-point messaging, note the following:

• Clients communicate with a queue destination.
• Messages are distributed to consumers in a serial fashion (first in, first out).
• Each message is delivered only to a single consumer.

123.Explain about “Topic Destinations”?
In JMS publish/subscribe messaging, the following is true:

• Clients communicate with a topic destination.
• Messages are broadcast to all subscribers.
• A message can be saved until at least one subscriber has consumed it (“durable”).

124.Explain about Threshold and Quotas in JMS?

• A threshold and a quota can be set for the server and destination objects.
• A quota is a limit defined for the JMS-administered objects; it includes the following values:
• The maximum number of bytes that can be stored
• The maximum number of messages that can be stored
• A threshold is a limit that triggers message paging, flow control, and logged warnings, using:
• Upper and lower values for the number of bytes
• Upper and lower values for the number of messages

125.Difference between “Durable Subscribers and Subscriptions”?

• Durable subscribers register durable subscriptions for guaranteed message delivery even if the subscribers are inactive.
• A subscriber is considered active if the Java object that represents it exists.
• By default, subscribers are nondurable.
• Administrators configure:
• Where the messages are persisted
• Persistent connection factories and destinations

126.What is “Persistent Messaging”?  When to Use it?

• Persistent messaging permits messages in memory to be written out to a persistent store.
• Configure persistent messaging if:
• Development requires durable subscriptions (use durable subscribers in the application)
• You require that in-progress messages persist across server restarts

127.How will you Configuring a Durable Subscription in Weblogic?

• To configure durable subscriptions, an administrator must:
• Create and configure a JMS store
• Configure connection factories or destinations as persistent
• Associate the JMS store with the JMS server
• The JMS store can be configured to use either:
• A file store
• A JDBC store (a connection pool)

128.How a Durable Subscription Works?

• If a subscriber client is active, messages are delivered normally.
• When the client becomes active again, its ID is used to retrieve and redeliver messages.

129.What Node manager can do in Weblogic server?
You can use Node Manager to:

• Start, shut down, and restart an Administration Server
• Start, shut down, suspend, and restart Managed Servers
• Automatically restart the Administration and Managed Servers on failure
• Monitor servers and collect log data