Transaction Log truncation is based on the Recovery Model that is set on the SQL Server database (use SQL Enterprise Manager - see Microsoft SQL Server documentation or do internet search on "changing SQL Server database recovery model")
SQL Server truncates the transaction log every time you back it up under the full or bulk-logged recovery model.
If you’re using the Simple Recovery model (which provides no transaction log recovery), SQL Server truncates the log at every transaction checkpoint.
If you are using the Full Recovery Model, see your DBA about increasing frequency that Fog database is backed up so the Transaction Log gets truncated -or- change over to the Simple Recovery Model.