Better understand VCB process steps

Hi,

I'am currently testing VCB 1.1 and my understanding of the product during the backup was:

Example: VM full Backup

- VCB initiate Snapshot  on VM

- The VM files are mount on VCB Proxy holding tank repository

- The backup software perform VM files' backup (into repository)

- At the end of backup the snapshot is committed to VM

But during my tests I saw that process is slightly different   

- VCB initiate Snapshot  on VM

- The VM files are mount on VCB Proxy holding tank repository

- The snapshot is removed

- The backup software perform VM files' backup (into repository)

My questions are:

- Could you please clarify VCB process steps (bullet point format)?

- Why the snapshots are "removed" before the backup of files into repository?

- What the steps "Release Disk Lease" do exactly ?

Thanks for your answers !!

Regards

Julien