Recovery Point Objective (RPO) describes a point in time that data can be restored from.
For instance, if there is data corruption, Data loss, at what point in time can a valid copy of the data be restored from? RPO is usually measured as minutes, hours, days, weeks, etc
If a database is corrupted then can we restore it back to what it was 30 minutes ago? This would be an RPO of 30 minutes.
Recovery Time Objective (RTO) is the amount of time which data or hardware is desired to be restored after a data corruption or hardware failure.
If a Database server just died. Time needed to bring it up and running again? If the answer is two hour then the Recovery Time Objective is two hour.
In a condition when a calamity occurs, the only main thing is to be bring the application available to users. There are many ways to make sure the applications can be brought back online like
1- Offline backup restoration
2- By using online replication method -- method to be available in case of Disaster
3- By using Mirroring /log shipping method – method to be available in case of Disaster
RTO and RPO needs to be defined with SLA(Service Level Agreement) to define the amount of data loss bearable in case of disaster and how much time is tolerable to get the services up and running.
