BDOC message flow and its architecture

Hi Expert,

It can be a simple question but i have a doubt regarding the flow of messages using SAP CRM middleware.

The scenario is like:

1. Message flows from ECC to CRM through a BDoc. (It can be opposite way also)

2. The BDoc fails in CRM due to some data issue.

3. A BDoc message id is generated.

4.Now the data is corrected in ECC and initial load was triggered.

5.The messages are flowing correctly.

So my doubt is:

1.What will happen to the old BDoc?

2. Do the initial or delta load processes the messages with new BDoc ID or through the old BDoc ID?

3. If the messages are processed through new BDoc id, can the old BDocs be deleted?

Please help me understand this concepts of BDocs and please provide me to some study material to get more undertsanding of the BDOC message flow architecture.

thanks,

Vicky