Datalog files created by the menu options are the same type of files as you create with the file i/o functions. Their data type reflects the controls and indicators of the front panel of the VI it was created with. There are two ways of reading one of these files:
1) You drop the VI you used to create the file on another VI, right-click it on the block diagram and select "enable database access". The "halo" showing up around the VI allows you to take particular records out of the file depending on an index or time stamp.
2) You use the file i/o functions, and wire a cluster to the "Open" function that exactly reflects the front panel of the VI you created.