The Exchange Processing Wizard will record the internal structure (folders) of mailboxes as part of the processing, which can result in large growth of the database due to amount of data being potentially processed. Depending on organisational size an increase between 20-35GB can be anticipated.
Customer are advised to size the disk holding the AD-LDS database accordingly.
In instances where the database is too large the following steps can be taken
i) Delete the legacy Exchange Processing wizard History
ii) Reduce the History retention Filter value from 100 to a smaller number (4 in this example)
iii) Follow the steps in https://blogs.technet.microsoft.com/isablog/2013/12/10/the-case-of-the-big-ad-lds-database/ to reduce databases where the increase in size has become problematic.