Least permission requirement for accessing pst file

Hello,

I am having an issue for User A in accessing Outlook data file when "Read" permission is assigned. It errors out saying access denied due to permission. However, if I assign Full permission to User B, we can open/add the Outlook data file with no issues. But my concern here is to give least level permission to the pst- not the full access. Else, what would be the use of "Read" permission?

Does anyone know the least permission requirement for granting access to user for any PST file on folder.

Thank you,

Arsh.