>What's the possible cause of consistently getting this problem?
>
>

Error: 9002, Severity: 17, State: 6
>The log file for database 'smartapp' is full. Back up the transaction log for the database to free up some log space.

>The manual says that we must do backup to free some log space but the drive where the transaction log resides have 60GB free space. We keep on doing the backup at least this day almost 5 times. Why? Why? Why?

Assuming SQL Server backend. You (the DBA) must run a back up of the database either with truncate transaction log or manually truncate the log after the back up. But the recovery mode must be set to simple for the truncate to work as you want. If it is set to full, the file will not shrink.

The other option is to let you transaction log grow. This assumes it is set to automatically grow and there is enough space on the disk to allow it.