Hi,
I am not sure if I got your question right ? Nevertheless I will try to answer your question.
Using Nokia PC Suite and Nokia DKU-5 cable you can transfer MIDlets directly to your mobile. During uploading the MIDlet you specify the .jad file name to upload. This file contains the information about the JAR file and its size, which is then uploaded into the mobile device.
For learning more about OTA, you can download a freely available tool called Deck IT from
PyWeb. It provides a WAP Emulator, which you can use to download MIDlet's from the wap sites and
test them.
Let me know if I understood the question.
Regards
Ritesh