When installing SSRS, there are two databases that get installed (default); ReportServer and ReporServerTempDB.
With SSRS, whether for SCCM or reporting in general, by default the ReportServer database Recovery model is enabled as FULL. Which means that all activity in the ReportServer database will get logged to the transaction file.
The side affect of this, the Transaction log file can get quite large with time. Recently, I assisted a client with a low disk space issue on a logical drive. After research, we determined that the ReportServer transaction log file had grown quite large… >60GB in size.
The fix? Change the ReportServer database Recovery model to Simple. To reclaim the space on disk, shrink the ReportServer transaction log file.
To back up the ReportServer database, and perhaps custom reports; DO enable regular database backups, here is one approach.
To change the recovery model, from SSMS, right click the ReportServer database > Properties. Click on Options, then change the Recovery Model to Simple. Then, OK.
To shrink the Transaction log file, right click the ReportServer database > Tasks > Shrink > Files
From the Shrink file dialog, choose file type of LOG. Shrink action of Release Unused space, then OK.
Note: Thanks Ken.