I am quite novice with DDBoost so forgive me if this question seems obvious.

When we look at RMAN stats, we see 'input size' and 'output size'.  When we look at DD stats, we see 'original bytes' and 'locally compressed'.  I am having a hard time making sense of RMAN Output Size vs DD Original Bytes.

My understanding is that RMAN Output Size is the size of the data to be backed up after unused blocks are excluded.  I found a post that stated 'if you are not using ddboost, original bytes is how much is sent over the network, global after dedupe and local after compression.'  But what does Original Bytes mean if you are using DDBoost and why would it be larger than RMAN Output Size?

Thanks