Any migration tool creates enormous load on servers, which many times exceeds normal load created even by a large number of users during regular server usage. No real user will ever create such avalanche of queries as a migration tool. It is not uncommon that server can be overloaded, have timeouts in response or even crash entirely in such situations.
In case your server is on-premises, we usually recommend to increase hardware (RAM and processor cores) on a server machine minimum twice before you start migration. However, in many cases it is not possible to upgrade hardware for various reasons, such as outdated or deprecated infrastructure, absent access to third party provider or due to other circumstances. In case of a cloud service an upgrade is principally impossible and cloud provider usually puts limitations on allowed load of service.
Enterprise Bridge uses elaborate techniques to overcome limitations in performance of servers or services involved into migration process. To leverage server load you can add pauses between copying of each page or document to decrease load on server and give it opportunity to recover. This setting allows defining such pauses in seconds. Default value is zero, which means no pauses. Please notice that non-zero values can considerably decrease migration speed.