Current limitations for log analysis (within log viewer):
- max 20 log files
- max 500 MB total log(s) size (in case of single log file analysis most recent 500 MB is analyzed, in case of multiple log file analysis you won't be able to start analysis if selection is greater then 500 MB)
It is described also here under "Current limitations": https://help.dynatrace.com/infrastructure-monitoring/log-analytics/what-insights-can-log-analytics-provide/
Limitations are valid for log analysis but not download.