TFA 18.4.1 (18.3.3 the same issue) is not working:
Cannot run diagcollect:
ora12c@uniw4dm1p:~$ /grid/app/12.1.0/grid/bin/tfactl diagcollect -srdc dbperf
Enter the Database Name [Required for this SRDC] : way4db
Do you have a performance issue now [Y|y|N|n] [Y]: n
Enter start time when the performance was bad [YYYY-MM-DD HH24:MI:SS] : 2018-12-05 12:50:00
Start time when the performance was bad: dec/05/2018 12:50:00
Enter stop time when the performance was bad [YYYY-MM-DD HH24:MI:SS] : 2018-12-05 13:30:00
Stop time when the performance was bad: dec/05/2018 13:30:00
For comparison, it is useful to gather data from another period with similar load where problems are not seen. Typically this is likely to be the same time period on a previous day. To compare to the same time period on a previous day enter the number of days ago you wish to use. [<RETURN> to provide other time range] : 1