In customer exits EXIT_SAPLCNAU_xxx (xxx = 001, 002 ...), messages are programmed with direct specification of the message category.
This results in different problems:
After the message has been processed, you exit the program.
Messages are processed often which is unnecessary.
In function modules EXIT_SAPLCNAU_xxx, the allowed message category is transferred in parameter SAP_MSGTY. If you want to process a message in the function module, this is only allowed if SAP_MSGTY is not initial. In addition SAP_MSGTY must always be assigned as a message category with the message statement.