Replicating Contacts from CRM to R/3

Guys,

We are trying to replciate contacts in CRM back to R/3 and the problem we are running into is R/3 creates too many dialog processes to update contact data in R/3 simultaneous. The question is how do I limit the update in R/3 to only one process?

Another question is when CRM replicates to R/3, does it use BDoc and is the update realtime or does these BDoc get placed in R/3 in some kind of BDoc queue?

Many thanks,

Yan.