If you know me well you will know that I really hate everything Blackberry.
Blackberry servers are well known for spanking the C drive space of your server.
They are normally located in
c:\program files (x86)\Research In Motion\Blackberry Enterprise Server\Logs
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What do you need to keep the logs for?
To free up space and stop BES from generating loads of space do the following :
Click on start, all programs, Blackberry Server Configuration
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Once open click on the cell to the right of Debug log daily file.
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Change the value to No.
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Click ok.
Restart the blackberry services and your good to go.