There are 2 types of flight log/record:
1) Flight log is a .TXT file that is generated by the Go4 app. It is what has seen the RC. It is easy to retrieve, you always get it but give only a partial view of what happen to the Spark.
2) Flight record is a .DAT file that can be retrieve from the Spark directly using the DJI assistant 2 software as explained
HERE. It need to power up and connect the Spark to a computer and it has a limited internal storage capacity for those files, typically only a few records. Also turning on/off the Spark create a record, so in case of a problematic flight, it is better to save the flight record directly. Advantage is that it has more info in it and is not affected by communication with the RC.
The flight log (TXT) can be sufficient for basic diagnostic and provide also a few extra info related to the RC or the gimbal.
The flight record (DAT) is more complete and gives information about the Spark attitude in the air (roll - pitch - yaw), compass ...
Flight log can be uploaded and viewed
HERE and the link easily shared. The flight log can be re-downloaded from that web site.
Flight log and Flight record can be processed by
CsvView and data plotted as graph.