I am not a big fan of the terms "Recovery Point Objective (RPO)" and "Recovery Time Objective (RTO)". I think that the terms "lost data" and "downtime" are much more descriptive and relevant.
That being said, the two are independent, not interchangeable or complementary. Both must be considered as any solution to increase system availability is evaluated.
When an interruption occurs, it can cause downtime, and it can cause lost data. The amount of downtime and lost data depend on the nature of the interruption, and the preventative/recovery methods that are in place.
An organization's requirements for minimizing downtime and lost data vary by application. Usually, that is determined by the cost to the organization of said downtime and lost data, and how much it is worth to protect against those factors.
I hope this is helpful. Thank you for the question.
This was first published in April 2003