TIBCO Enterprise Message Service Interview Questions

1. What are the messaging models does EMS support?
a. Point-to-Point (Queue)
b. Publish and Subscribe (Topic)
c. Multicast (Topic)
2. What are the limitations of the Durable Subscriber?
• As long as the durable subscriber exists
• Expiration time of the message
• Storage limit of that Topic
3. What is the difference between "Multicasting" and "publish and subscribe" messaging model?
4. What are the EMS Destination features?
• Secure Property
• Trace Property
• Store Property
• Redelivery policy
• Flow control
• Exclusive property for queues
5. What are the extra features are available in EMS apart from JMS?
• The JMS standard specifies two delivery modes for messages, PERSISTENT and NON_PERSISTENT. EMS also includes a RELIABLE_DELIVERY mode that eliminates some of the overhead associated with the other delivery modes.
• For consumer sessions, you can specify a NO_ACKNOWLEDGE mode so that consumers do not need to acknowledge receipt of messages, if desired. EMS also provides an EXPLICIT_CLIENT_ACKNOWLEDGE and EXPLICIT_CLIENT_DUPS_OK_ACKNOWLEDGE mode that restricts the acknowledgement to single messages
• EMS extends the MapMessage and StreamMessage body types. These extensions allow EMS to exchange messages with TIBCO Rendezvous and ActiveEnterprise formats that have certain features not available within the JMS MapMessage and StreamMessage
6. What is structure of JMS Message?
• Header(Required)
• Properties(optional)
• Body(optional)
7. Where does the undelivered messages will be stored?
• If a message expires or has exceeded the value specified by the maxRedelivery property on a queue, the server checks the message’s JMS_TIBCO_PRESERVE_UNDELIVERED property. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to true, the server moves the message to the undelivered message queue, $sys.undelivered. This undelivered message queue is a system queue that is always present and cannot be deleted. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to false, the message will be deleted by the server
• You can only set the undelivered property on individual messages, there is no way to set the undelivered message queue as an option at the per-topic or per-queue level
8. What are the messages bodies are supported by the EMS?
• Map Message
• Text Message
• Stream Message
• Bytes Message
• Object Message
9. What is the Maximum message size is supported by EMS?
EMS supports messages up to a maximum size of 512MB. However, we recommend that application programs use smaller messages, since messages approaching this maximum size will strain the performance limits of most current hardware and operating system platforms
10. What are the different delivery modes available in EMS?
• Persistent
When a producer sends a PERSISTENT message, the producer must wait for the server to reply with a confirmation. The message is persisted on disk by the server. This delivery mode ensures delivery of messages to the destination on the server in almost all circumstances. However, the cost is that this delivery mode incurs two-way network traffic for each message or committed transaction of a group of messages
• Non-Persistent
Sending a NON_PERSISTENT message omits the overhead of persisting the message on disk to improve performance.
If authorization is disabled on the server, the server does not send a confirmation to the message producer.
If authorization is enabled on the server, the default condition is for the producer to wait for the server to reply with a confirmation in the same manner as when using PERSISTENT mode.
Regardless of whether authorization is enabled or disabled, you can use the npsend_check_mode parameter in the tibemsd.conf file to specify the conditions under which the server is to send confirmation of NON_PERSISTENT messages to the producer

• Reliable
EMS extends the JMS delivery modes to include reliable delivery. Sending a RELIABLE_DELIVERY message omits the server confirmation to improve performance regardless of the authorization setting.
When using RELIABLE_DELIVERY mode, the server never sends the producer a receipt confirmation or access denial and the producer does not wait for it. Reliable mode decreases the volume of message traffic, allowing higher message rates, which is useful for messages containing time-dependent data, such as stock price quotations.
11. If a persistent message is published on to a TOPIC, Does these messages will store on disk if topic doesn’t have durable subscriber or subscriber with a fault-tolerant connection?
No. Persistent messages published to a topic are written to disk only if that topic has at least one durable subscriber or one subscriber with a fault-tolerant connection to the EMS server. In the absence of a durable subscriber or subscriber with a fault-tolerant connection, there are no subscribers that need messages resent in the event of a server failure. In this case, the server does not needlessly save persistent messages. This improves performance by eliminating the unnecessary disk I/O to persist the messages

12. What are the different types of acknowledgement modes in EMS message delivery?
• Auto
• Client
• Dups_ok
• No_ack
• Explciit
• Explicit_client_dups_ok
• Transitional
• Local transitional.
13. What are the different types of messages that can be used in EMS
• Text
• Simple
• Bytes
• Map
• XML test
• Object
• Object ref
• Stream
14. Tell me about bridges. Why do we use them, Syntax to create bridges, use of message selector?
• Some applications require the same message to be sent to more than one destination possibly of different types. So we use bridges in that scenario.
• create bridge source=type:dest_name target=type:dest_name [selector=selector]

15. What is the purpose for stores.conf
• This file defines the locations either store files or a database, where the EMS server will store messages or metadata. Each store configured is either a file-based or a database store.
16. How many modes are the messages written to store file.
• Two Modes: Synchronous and Asynchronous
• Default is asynchronous
17. What is tibemsd.conf
• It is the main configuration file that controls the characteristics of the EMS server
18. Name destination properties and explain them.
• Global, secure, maxmsgs, maxbytes, flowcontrol, sender_name, sender_name_enforced, trace,maxRedelivery
19. What are the different modes of installation in Ems?
• GUI mode
• Console mode
• Silent mode
20. What are the messaging models supported by JMS
• Point-to-point
• Publish-subscribe
• Multicast
21. What is the use of routes? What kind of destinations can be used in routes?
• Topics and queues m-hops

22. What happens if the message expires/exceeded the value specified by maxredelivery property on queue?
• If the jms_preserve_undelivered property is set to true, then it moves he message to undelivered message queue, if set to false, the message is deleted by the server.
23. In how many ways can a destination be created?
• Static-created by server
• Dynamic-created by client
• Temporary destinations.
24. What are the wild cards that we use in ems? how do they work for queues and topics
• *,> you can subscribe to wildcard topics but can’t publish to them. Where as in case of queues we can’t either send /receive.

25. Is bridges are transitive?
• NO
26. Tell me about flow control on destinations
• Some times the producer may send messages faster than the consumers can receive them. So, the message capacity on the server will be exhausted. So we use flow control. Flow control can be specified on destinations.
27. Tell me about flow control on bridges and routes
• Flow control has to be specified on both sides of bridges where as on routes it operates differently on sender side and receiver side.
28. Name 3 configuration files and tell me what it consists of
• Queues.conf
• Topics.conf
• Routes.conf
• Factories.conf
• Stores.conf
• Groups.conf,users.conf,transports.conf
29. Name some administrative level destination properties
• View
• Create
• Delete
• Modify
• Purge
30. How can you change the configuration properties of EMS server?
• You can change in the tibemsd.conf file or you can change using the ems admin console.
31. What are the permissions that you can grant to users to access queues
• Receive
• Send
• Browse
32. What are the permissions that you can grant to users to access topics
• Subscribe
• Publish
• Durable
• Use_durable
33. Tell me about multicasting in EMS
• Multicast is a messaging model that broadcasts messages to many consumers at once rather than sending messages individually to each consumer. EMS uses Pragmatic general multicast to broadcast messages published to multicast enabled topics.
• Each multicast enabled topic is associated with a channel.
34. What are the advantages and disadvantages of multicasting?
• Advantages: as the message broadcasts only once thereby reducing the amount of bandwidth used in publish and subscribe model. Reduces the network traffic.
• Disadvantages: Offers only last-hop delivery. So can’t be used to send messages between servers.
35. On what destinations can you use multicast?
• Topics
36. Suppose, you got an error while accessing a queue, that you don’t have necessary permissions to access the queue. What might be the solution/reason?
• The user that is assigned to the queue and the user used while creating
37. How does the secondary server know that the primary server is failed?
• Based on heartbeat intervals
38. What is JMS queue requestor?
• The JMS Queue Requestor activity is used to send a request to a JMS queue name and receive a response back from the JMS client
39. What is JMS topic requestor?
• The JMS Topic Requestor activity is used to communicate with a JMS application’s request-response service. This service invokes an operation with input and output. The request is sent to a JMS topic and the JMS application returns the response to the request.
40. How do you add ems server to administrator?
• Using domain utility
41. How do you remove individual messages from destinations?
• Use Puge Command.
42. What are the messaging models does EMS support?
• Point-to-Point (Queue)
• Publish and Subscribe (Topic)
• Multicast (Topic)
43. What are the limitations of the Durable Subscriber?
• As long as the durable subscriber exists
• Expiration time of the message
• Storage limit of that Topic
44. What is the difference between "Multicasting" and "publish and subscribe" messaging model?
45. What are the EMS Destination features?
• Secure Property
• Trace Property
• Store Property
• Redelivery policy
• Flow control
• Exclusive property for queues
46. What are the extra features are available in EMS apart from JMS?
• The JMS standard specifies two delivery modes for messages, PERSISTENT and NON_PERSISTENT. EMS also includes a RELIABLE_DELIVERY mode that eliminates some of the overhead associated with the other delivery modes.
For consumer sessions, you can specify a NO_ACKNOWLEDGE mode so that consumers do not need to acknowledge receipt of messages, if desired. EMS also provides an EXPLICIT_CLIENT_ACKNOWLEDGE and EXPLICIT_CLIENT_DUPS_OK_ACKNOWLEDGE mode that restricts the acknowledgement to single messages
• EMS extends the MapMessage and StreamMessage body types. These extensions allow EMS to exchange messages with TIBCO Rendezvous and ActiveEnterprise formats that have certain features not available within the JMS MapMessage and StreamMessage
47. What is structure of JMS Message?
• Header(Required)
• Properties(optional)
• Body(optional)
48. Where does the undelivered messages will be stored?
• If a message expires or has exceeded the value specified by the maxRedelivery property on a queue, the server checks the message’s JMS_TIBCO_PRESERVE_UNDELIVERED property. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to true, the server moves the message to the undelivered message queue, $sys.undelivered. This undelivered message queue is a system queue that is always present and cannot be deleted. If JMS_TIBCO_PRESERVE_UNDELIVERED is set to false, the message will be deleted by the server
• You can only set the undelivered property on individual messages, there is no way to set the undelivered message queue as an option at the per-topic or per-queue level
49. What is the Maximum message size is supported by EMS?
• EMS supports messages up to a maximum size of 512MB. However, we recommend that application programs use smaller messages, since messages approaching this maximum size will strain the performance limits of most current hardware and operating system platforms
50. What are the different delivery modes available in EMS?
• Persistent
when a producer sends a PERSISTENT message, the producer must wait for the server to reply with a confirmation. The message is persisted on disk by the server. This delivery mode ensures delivery of messages to the destination on the server in almost all circumstances. However, the cost is that this delivery mode incurs two-way network traffic for each message or committed transaction of a group of messages
• Non-Persistent
Sending a NON_PERSISTENT message omits the overhead of persisting the message on disk to improve performance.
If authorization is disabled on the server, the server does not send a confirmation to the message producer.
If authorization is enabled on the server, the default condition is for the producer to wait for the server to reply with a confirmation in the same manner as when using PERSISTENT mode.
Regardless of whether authorization is enabled or disabled, you can use the npsend_check_mode parameter in the tibemsd.conf file to specify the conditions under which the server is to send confirmation of NON_PERSISTENT messages to the producer
• Reliable
EMS extends the JMS delivery modes to include reliable delivery. Sending a RELIABLE_DELIVERY message omits the server confirmation to improve performance regardless of the authorization setting.
When using RELIABLE_DELIVERY mode, the server never sends the producer a receipt confirmation or access denial and the producer does not wait for it. Reliable mode decreases the volume of message traffic, allowing higher message rates, which is useful for messages containing time-dependent data, such as stock price quotations.
51. If a persistent message is published on to a TOPIC, Does these messages will store on disk if topic doesn’t have durable subscriber or subscriber with a fault-tolerant connection?
• No. Persistent messages published to a topic are written to disk only if that topic has at least one durable subscriber or one subscriber with a fault-tolerant connection to the EMS server. In the absence of a durable subscriber or subscriber with a fault-tolerant connection, there are no subscribers that need messages resent in the event of a server failure. In this case, the server does not needlessly save persistent messages. This improves performance by eliminating the unnecessary disk I/O to persist the messages