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Introduction to IBM MQ – Part 2

Introduction to IBM MQ

Part 2

MQ Object Naming Conventions

Some of the rules for naming MQ objects such as queue managers and queues are given below :

  • Names of the MQ objects listed below are limited to 48 characters.

Queue managers, Queues, Process definitions, Namelists, Clusters, Listeners, Services, Authentication information objects and Topics and subscriptions

  • MQ Object names should have these character set :    A-Z,a-z,0-9, and the characters . / % _
  • MQ channel names should have a maximum of 20 characters
  • Object names that begin with “SYSTEM” are reserved
  • Names are case sensitive
  • The rules for naming MQ objects are the same on all supported operating systems. No implied structure exists in a name that you might find in the rules for file names on many operating systems
  • Agree with all stake-holders regarding all MQ object names before implementing the MQ project.
  • Embedded or leading blank characters are not allowed in object names

MQ Messages

A message is any information that one application uses to communicate to another. A message can convey a request for a service, or it can be a reply to a request. A message might also report on the progress of another message: to confirm its arrival or report on an error, for example. A message can also carry information for which no reply is expected.

Parts of MQ messages

 

  • Application Data – Content and structure defined and understood by the application program
  • Header or Message Descriptor (MQMD) – Contains control information like type of message and priority which are understood and used by MQ
  • Can contains optional headers that contain information about message structure, intended consumers, and message properties

Other aspects of MQ Messages

  • Default length is 4 MB; the max length is 100 MB
  • Length can be restricted by the definition of MQ objects and the system storage
  • Messages can be segmented or grouped

Headers typically contain elements like:

  • Unique Message Id
  • Routing information
  • Message format

Few examples of the application data part of a message:

  • A row from a DB2 table
  • A record from an indexed or flat file
  • Individual columns from DB2 tables
  • Multiple rows or records

MQ Message Descriptor (Header) has the following info :

  • Message ID/Correlation ID
  • Date and time
  • Persistent/Non persistent
  • Version
  • Priority
  • Life time of a message
  • Coded Character Set Id
  • Format
  • Sender application and type
  • Segmentation/Grouping information
  • Report options/Feedback
  • Back out counter

MQ Message Types

Based on Retention Types, messages can be :

  • Persistent
  • Non-persistent

Functionally, MQ Messages can be :

  • Datagram
  • Request
  • Reply
  • Report

 

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