There are two methods by which you can split PST files.
1). Manual method : You can split PST files through manual method but it has a high risk of loosing your data as it is not a risk free tool and takes a lot of time to split.
2)..Professional method : Aryson Split PST Software is a professional for splitting oversized Outlook PST files into smaller PST. It can split up single or multiple files very easily. It can split large PST file like, emails, contacts, calendars, journals, notes, tasks, etc. into smaller PST files.