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