Install OJS in database

Hi, Tell me, Which is more better way for install OJS for 3 diferents journals?

Should I install ojs in different database for each journal or install OJS in a single database for all journals?

You can easily have 3 journals on one installation of OJS. If editorial boards want to be completely separated than you can have 3 installations of OJS and put one journal in each installation.
I hope this helps.