Scheduling the relocation of archive logs

Because they are the primary mechanism for recovering from data corruption, database logs are normally kept on premium storage, both for I/O performance and data reliability reasons. Even after they have been archived, logs are normally kept online for fast recovery, but the likelihood of referring to an archived log decreases significantly as its age increases. This suggests that archived database logs might be relocated to lower-cost volumes after a certain period of inactivity.

The rapidly decaying probability of use for archive logs suggests that regular enforcement of a placement policy that relocates them to lower-cost storage after a period of inactivity can reduce an enterprise's average cost of online storage.

For example, a customer could be using a large DB2 database with thousands of active sessions, which needs to be up and running 24 hours a day and seven days a week with uptime of over 99%, and the database generates a large number of archive logs per day. If the database goes down for any reason, there is business requirement to bring the database back online and functional with in 15 minutes. The archive logs need to be created in a fast EMC array. Archive logs older than a week can be moved to a mid-range Clarion array. Archive logs older than 15 days can be moved slow JBOD disks. The database administrator purges the archive logs after 30 days. To set up a policy like this, see the following example. Assume that archive logs are created on the file system, /proddb_archlog, using DB2 commands.

To add the NEW, MEDIUM, and OLD storage classes

To convert the database's file system and add volumes for use with Database Dynamic Storage Tiering

To classify volumes into storage classes

Once the volumes are configured, an administrator can define file placement policy rules that specify access age-based relocation of selected files and assign them to the database's file system.

To define rules that periodically relocate archive logs

Database Dynamic Storage Tiering translates these commands into DST access age-based policy rules, merges them with the file system's placement policy, and assigns the resulting policy to the file system. By default, Database Dynamic Storage Tiering enforces the active policy daily. During enforcement, the new rules relocate qualifying files to the destination storage tiers specified in the dbdst_file_move commands used to create the policies.