This graph shows the aggregated space used within all database transaction logs on a given instance of SQL Server for the selected date range. This metric is useful for determining if issues may be occurring due to log space consumption. These include, lack of log space issues, log backups not running on a suitable frequency and the occurrence of transactions affected large amounts of data.
If you notice significant spikes in log growth this may be caused by database maintenance. RockSolid index maintenance should be used as this includes logic to minimise log growth during maintenance windows. If RockSolid index maintenance is being used, you may also consider switching to defragmenting indexes instead of rebuilding indexes to resolve log space issues incurred during index maintenance windows.