1) - Database Compaction
The primary purpose of database compaction is to free up unused space within the database file (however, it should be noted that this does not return that unused space to the file system). The intention is to free up pages in the database by compacting records onto the fewest number of pages possible, thus reducing the amount of I/O necessary.
2) - Database Defragmentation
(make the IO more sequential as opposed to random) as well as to maintain the compactness of tables marked as sequential.
3) - Database Checksumming
Database checksumming (also known as Online Database Scanning) is the process where the database is read in large chunks and each page is checksummed (checked for physical page corruption). Checksumming’s primary purpose is to detect physical corruption and lost flushes that may not be getting detected by transactional operations (stale pages).
4) - Page Patching
Page patching is the process where corrupt pages are replaced by healthy copies. As mentioned previously, corrupt page detection is a function of database checksumming (in addition, corrupt pages are also detected at runtime when the page is stored in the database cache)
5) - Page Zeroing
Database Page Zeroing is the process where deleted pages in the database are written over with a pattern (zeroed) as a security measure, which makes discovering the data much more difficult.
URL: - http://blogs.technet.com/b/exchange/archive/2011/12/14/database-maintenance-in-exchange-2010.aspx