I get message "The statement BACKUP LOG is not allowed while the recovery model is SIMPLE ...".

If a database's recovery model is simple, such as master , model .etc system databases , it has no transaction log file , you can only do full and differential backup on this type of database.

But if you change database's recovery model to full or Bulk-logged , you can create transaction log backup from this database.

Following step show how the change a database's recovery mode :

  1. Open SQL Management Studio.
  2. Mouse right click on the database and select "Properties" item in the pop menu.
  3. In the properties widow , select the "Options" ,then change recovery model