This is an excerpt from my free eBook, Brad’s Sure Guide to SQL Server 2008, which can be downloaded here.
As DBAs, one of our goals is to separate OLTP (On-Line Transaction Processing) and OLAP (On- Line Analytical Processing) activity, preferably onto different servers. This is because performing both types of activities in the same database, or even in different databases on the same server, can lead to performance problems. In order to accomplish this goal, DBAs must figure out the best way to move transactional data from OLTP servers to servers designated for OLAP activity so that the data remains more or less synchronized. This sounds simple, but can prove to be difficult in practice.