The message identifier you specify on the Add Message Description (ADDMSGD) command is used to refer to the message and is the name of the message description.
The message identifier must be 7 characters:
pppmmnn
where ppp is the product or application code, mm is the numeric group code, and nn is the numeric subtype code. The number specified as mmnn can be used to further divide a set of product or application messages. Numeric group and subtype codes consist of decimal numbers 0 through 9 and the characters A through F.
For example, the following is message 1234 of CPF.:
CPF1234
When you create your own messages, using the letter U as the first character in the product code is a good way to distinguish your messages from system messages. For example:
USR3567
The first character of the code must be alphabetic, the second and third characters can be alphanumeric; the group code and the subtype code must consist of decimal numbers 0 through 9 and the characters A through F. Note that although this range can be called a set of hexadecimal numbers, any sorting of the message numerics treats A through F as characters.
For example, when displaying a range of message descriptions, CPFA000 precedes CPF1000.
You should use care in using a numeric subtype code of 00 in the message identifier. If you use a numeric subtype code of 00 for a message that can be sent as an escape, notify, or status message and that can, therefore, be monitored, a subtype code of 00 in the Monitor Message (MONMSG) command causes all messages in the numeric group to be monitored.