In every Amiga system, the ENVARC: assign should point to SYS:Prefs/Env-Archive/ directory. ENV: points to ram:env/.
So, ENVARC: is used to store data permanently while ENV: is reseted in reboot.
Check ENVARC:Mediator/NoCache (or SYS:Prefs/Env-Archive/Mediator/NoCache) file with some text editor (ED for example). If the file exists, change the first line to Yes if it's set to No. If the file doesn't exist, you can create it by typing that Yes to text editor and saving the file.
Other way to set the variable is to type in shell:
setenv Mediator/NoCache SAVE Yes
That's the "official" way to set variables, but OTOH, it loses the other information stored in the file. NoCache (as well as other Mediator config files in env) file should contain some help lines inside it by default, so I'd recommend the text editor way.
And in any case, I'd say you should read through all the files in ENVARC:Mediator/. They have pretty good explanations in each.
