The purpose of the policy engine in a data archiving environment is to automate the process of moving the appropriate data from primary storage into archive storage. It does this by monitoring data access patterns in primary storage and automatically moving the data that is least accessed into an archive storage device. This process allows for more efficient use of primary storage and also reduces storage costs.

Cloud tiering is a technology that automatically moves inactive or infrequently accessed data from high-performance primary storage to lower-cost secondary storage, such as cloud-based object storage. This process is based on policies that are defined by the IT administrator. Cloud tiering is a part of the secondary storage tier, which is typically used for storing inactive or infrequently accessed data that does not require the high performance or low latency of primary storage. The primary storage tier is used for storing active or frequently accessed data that requires high performance and low latency. The application tier is used for hosting applications and services, while the policy tier is used for defining and enforcing data management policies. Reference: Section 4.4 Secondary Storage Tier, page 239.