There's a few ways that come to my mind, you could e.g. set all SCEUSER in F98OWSEC to 02 (=disabled), except for JDE or other system users. With backups obvs., or setting an unused column so you can find your entries later on, Truncate the table completely... etc.pp. SQL gives you a lot of power here and it's very safe if you kill all sessions after doing so.
Depending on the amount you could also expire all their roles, except for SYSADMIN, take away their possibility to connect (as in shut down HTML instances and development clients or by network) etc.pp.