MQ Series Interview Preparation Guide

The following are some of the reserved queue names of IBM Websphere MQ Series
SYSTEM.ADMIN.CHANNEL.EVENT Queue for events of channel
SYSTEM.ADMIN.COMMAND.QUEUE Queue for PCF command messages to be sent for
non- z/OS
SYSTEM.ADMIN.CONFIG.EVENT Queue for events of configuration
SYSTEM.ADMIN.PERFM.EVENT Queue for events of performance
SYSTEM.ADMIN.QMGR.EVENT Queue for events of queue manager
SYSTEM.CHANNEL.COMMAND A distributed queuing queue on z/OS using CICS
SYSTEM.CHANNEL.INITQ A distributed queuing queue on z/OS without CICS
SYSTEM.CHANNEL.SEQNO A distributed queuing queue on z/OS using CICS
SYSTEM.CHANNEL.SYNCQ A distributed queuing queue on z/OS without CICS
SYSTEM.CICS.INITIATION.QUEUE Queue for utilization of triggering for non- z/OS
SYSTEM.CLUSTER.COMMAND.QUEUE Queue for communication repository changes among queue managers (applicable for AIX, HP-UX, Linux, OS/2 Warp, OS/400, Solaris, Windows, and z/OS only)
SYSTEM.CLUSTER.REPOSITORY.QUEUE Queue for holding information about repository (applicable for AIX, HP-UX, Linux, OS/2 Warp, OS/400, Solaris, Windows, and z/OS only)

- MQ is operating system independent - MQ is protocol independent – supports TCP/IP, LU6.2, SNA, NetBIOS,UDP - Sender and receiver can be from any platform

- The exchanging of messages among sending and receiving programs is time independent
- The sending and receiving application programs are decoupled
- Sender’s process can continue with out the need of waiting for the receiver’s acknowledgement message
- The receiver’s application need not be running while the message is sent
- The receiver can retrieve the messages after it has been started

- Persistent messages are usually logged.
- The performance of the application is reduced by logged messages
- Persistent messages are utilized only for essential data
- When the queue manager is stopped / failed or the data in the message is discarded, then use a non persistent message.
- As the logged data is persisted for long time and need to keep track about the events that are happening in the systems, this data need to be persisted
- Use buffering mechanism to improve the speed of retrieving data from the logged messages

MS Windows Operating System: The configuration information of Queue Manager is stored in the Windows Registry
UNIX Operating System:
1. At the time of product installation, the Web Sphere Message Queue configuration is created.
A list of queue managers are available the list is updated every time a queue manager is deleted or created.
Each node has only one ‘mqs.ini’ file
2. At the time of creating a new queue manager, a file with extension ‘qm.ini’ is created automatically.
It contains configuration parameters for the queue manager

To start the Queue Manager: strmqm QMName
To stop the Queue Manager: endmqm -w QMName

The following are the types of queues:
1. Model Queue: A queue definition is called a model queue. It is used when a dynamic queue is created
2. Alias Queue: Another name for a local queue or a remote queue. It’s usage is for security and maintenance
3. Remote Queue: Remote queue is a queue definition pertaining to another Q Manager
4. Initiation Queue: It is a local queue. Queue manager writes a trigger message at the time of meeting certain conditions on another local queue
5. Dynamic Queue : A dynamic queue is created ‘on the fly’ on demand by the application. The dynamic queues may be retained or automatically deleted when the application program ends. It is used to store any intermediate result
6. Cluster Queue: A local queue. It is known throughout a cluster of queue managers
7. Reply-to-queue: A request message must have the queue name, into which the program that is responding must put the reply message

- The message can be retrieved in First-in-first-out (FIFO) basis.
- Message priority – defined in the message descriptor. Messages with same priority are retrieved on a FIFO basis
- A specific message can be retrieved by a program request.

- An application which starts in response to an event that is triggered in MQ Queue Manager is defined as a process definition
- The application ID, application type and data specific to the application are the attributes for defining process definition

MQ messages types are:
- Datagram – It is an unsolicited message
- Request - A message for which a response is expected
- Reply – A message event such as a confirmation on arrival or delivery. It can be an error
MQ messages can be persistent or non-persistent