Format of message data
We can specify any of the following:
- The format of the application data
- The character set of the character data
- The format of numeric data
To do this, use these fields:
- Format
- This indicates to the receiver of a message the format of the application data in the message.
When the queue manager creates a message, in some circumstances it uses the Format field to identify the format of that message. For example, when a queue manager cannot deliver a message, it puts the message on a dead-letter (undelivered message) queue. It adds a header (containing more control information) to the message, and changes the Format field to show this.
The queue manager has a number of built-in formats with names beginning MQ, for example MQFMT_STRING. If these do not meet your needs, we can define your own formats (user-defined formats), but not use names beginning with MQ for these.
When you create and use your own formats, write a data-conversion exit to support a program getting the message using MQGMO_CONVERT.
- CodedCharSetId
- This defines the character set of character data in the message. If you want to set this character set to that of the queue manager, we can set this field to the constant MQCCSI_Q_MGR or MQCCSI_INHERIT.
When you get a message from a queue, compare the value of the CodedCharSetId field with the value that your application is expecting. If the two values differ, you might need to convert any character data in the message or use a data-conversion message exit if one is available.
- Encoding
- This describes the format of numeric message data that contains binary integers, packed-decimal integers, and floating point numbers. It is usually encoded according to the particular machine on which the queue manager is running.
When you put a message on a queue, you usually specify the constant MQENC_NATIVE in the Encoding field. This means that the encoding of your message data is the same as that of the machine on which your application is running.
When you get a message from a queue, compare the value of the Encoding field in the message descriptor with the value of the constant MQENC_NATIVE on your machine. If the two values differ, you might need to convert any numeric data in the message or use a data-conversion message exit if one is available.
Parent topic:
Format of message control information and message data
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