Difference between "SYSADM" and "SYSDBA"

SYSADM is typically a user (schema) in the Oracle database that contains the tables, indexes, etc. required to support a Peoplesoft application.

SYSDBA is a special role in the Oracle database that lets someone start and stop the database (among other special tasks). The SYSDBA role is granted to a specific user in order to let that user perform those tasks assigned to that role.