SQL Log Space Rules
These Rules monitor the amount of used transaction log space in the SQL Server (including both data and transaction log).
SQL-DMO library must be installed on the monitoring engine. It is generally installed as part of SQL Server client package, but do check sqldmo.dll is in drive:\Program Files\Microsoft SQL Server\80\Tools\Binn
You can monitor the whole of the SQL Server on the machine, or individual databases. You can use absolute values (in MB, GB, etc.) or percentages.
By default, the Rule will recalculate statistics before obtaining the database space usage. Optionally, this recalculation can be skipped thus making faster (but less precise) readings.