The SharePoint farm administrator must minimize the impact of upgrading a MOSS 2007 farm to SharePoint 2010. How long this process takes is dependent on the size of the installation.
MOSS 2007 SP2 installed a new capability that allows an administrator to set the content database to read-only. The result of this is that users can only read from the database and cannot perform any write operation.
The advantage of this when doing an upgrade is that users can continue using the MOSS 2007 farm while the data is being upgraded on the SharePoint 2010 farm.
This recipe shows how to set a database as read-only.
WSS 3.0/MOSS 2007 installation must have the Office 2007 Service Pack 2 installed.