Query Processing in Tertiary Memory Databases

Wit,11 rapid increase in the number of applica-tions thal, require access to large amounts of da,ta., it is becoming increasingly important for tla.ta.l~aac syst,ems t,o ha.ndle tert,ia.ry storage dcviccs. The cha.ra.ctcristics of tertia.ry mem-ory devices a.re very differ & from secondary storag;c devices that, conventional database sysletr ~ a.re designed for. This requires new approa.ches to ma.naging data, loca.tion and movcmcnt, together with query execution in a unilied framework. In this paper WC present methods of scheduling queries, caching and controlling the order of da.ta, rct,rieva.l for eff~-c&1. operation in a tertia.ry rncniory cnviron-nienl. Wc show how careful interspersing of queries and informed cache management can achieve rema.rkable reductions in access time compared 1x1 conventional methods. Our al-goril(hms use a few model pa.rameters for each tertiary memory device and are thus designed to be portable across a wide variety of tert,ia.ry memory devices and da,tnhase t,ypes. We arc extending the PoS’TGR.ES database system to implements t,he new query processing strate-gics. Jnit,ial mea.surements on the prototype yield impressive results