In database systems, there is a strong tendency for a relatively small proportion of data to be hot data and the majority of the data to be warm or cold data. These sets of multi-temperature data pose considerable challenges if you want to optimize the use of fast storage by trying not to store cold data there. As a data warehouse consumes increasing amounts of storage, optimizing the use of fast storage becomes increasingly important in managing storage costs.
Storage groups are groups of storage paths with similar qualities. Some critical attributes of the underlying storage to consider when creating or altering a storage group are available storage capacity, latency, data transfer rates, and the degree of RAID protection. You can create storage groups that map to different classes of storage in your database management system. You can assign automatic storage table spaces to these storage groups, based on which table spaces have hot, warm, or cold data. To convert database-managed table spaces to use automatic storage, you must issue an ALTER TABLESPACE statement specifying the MANAGED BY AUTOMATIC STORAGE option and then perform a rebalance operation.
Because current data is often considered to be hot data, it typically becomes warm and then cold as it ages. You can dynamically reassign a table space to a different storage group by using the ALTER TABLESPACE statement, with the USING STOGROUP option.