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Weblogic Application Server FAQs

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