If this visa has expired or it about to expire one must apply for a Resident Return Visa sc155. This visa is granted automatically to resident who have been onshore for more than 730 days.
For PR visa holders who have had to leave Australia before being onshore for more than 730 days, and the PR visa has expired. Depending on their circumstances may still apply for this visa. This application is more detailed.
The RRV is essentially an extension of the PR visa. They are generally granted for a 5-year period.