We recently deployed Outlook Web Access (OWA) for all our users. Although we haven't noticed an increase in mail traffic, the number of transaction log files is increasing much faster than it did before our users began using OWA. What's causing this increase?
Enabling OWA can have the hidden side effect of increasing your transaction log count. When users use OWA's Search function, Exchange Server creates indexes for the search criteria. As a result, performing several searches will create a lot of new indexes, and each new index adds a bit of information to the log file. The more messages that a search finds, the bigger the index—for example, a search that finds 500 items will add, on average, 1MB to 2MB to the log file. Because log files are always 5MB in size, you'll notice more log files if your users perform large searches or several searches.