PGA: For every user who connects to database they have a dedicated PGA. PGA is Program Global Area. In PGA there is the hash code and session variable of that user.

UGA: User Global Area. If there is a dedicated server process for each user the UGA will be a part of PGA. If there is s shared sever process (there can be, industries sometimes use it for cost cutting) the UGA will be part of PGA.

dba_%

select table_name from dict where lower(table_name) like 'dba%';

static views are in prural (s). dynamic views are in singular