You must be new to the IMS DC world. The boys were right in sending you to the manuals. There is a lot to learn. The manuals will tell you what they are. However what they may not tell you is that the use of PURG is discouraged except for special circumstances. What it does is it explicitly tells IMS to transmit all pending message segments rather than letting the program end normally or issuing an additional GU call on the IO PCB.
I would not code this into a program without getting approval. Letting IMS do its job in a normal fashion is desirable for maintenance purposes if nothing else.
