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Show 9 2.5.1 Cricket C ri cket [I 9] is a research prototype tbat was developed at the Uni versity of Wis<U IJs iJ J. lVLulison. It uses Mach's ext<~ r na l pager facility to map memory into a JJser "'s address space and prov ides transparent persistence. ( 'r icket uses virt ual add resses as object ident ifie rs. It uses the memory management primit ives of th -. l\llach op<~ rat i ng system [2] to p rovide the abst raction of a s!Jctr<'d, transacLion<il, si JJgle-lc· vcl store that can lw d irectly accessed by a user applic<tt io n. T lw cl ieJJt t reaLs a database as a memory o bject with the Cricket S(Jr v<'J playing the role of its exterual pager. It therefore imposes a limi t of ;32 bi ts on tlw virtual address space oC the clat<thase. Cricket a lways maps a database to tlw sarne range of virt ua l addresses and database I/ 0 is com p letely transparent to client applications. [ t can not r<~solve the vir t u al memory confl icts among multiple da.tabast-·s t ha.L map to t h <'~ same or overl apping ad dresses. As a res ul t of Cri cket 's implementat ion as a Mach 's externa l pager , concurrency coJlt ru l et.tlcl r<-~cov<-~ ry are a lso t rans pct.ren t to c lie nt ap pli catio ns. Cricket prov ides 1 wo-p hase, page- level locking for cli ents. lt Jdex mauagernenL, rf'covery, and di st ribu t ion a re st ill among t he unresolved d<'sign iss nes. 2.5.2 Exodus Storage Manager The Exod us ~ to rage Ma nager ( ESl\11) [15] was developed at the Uni vers ity of Wiscon s in. l\llacli son . It provid<~s a. sd of bas ic facilities for 11se across a ll <Lppli caLions. In CSi\1!, th<-' O lD of an o bject co nsists of a Lj byte page number , 2 byte slot J1llmher iJJ s icle the page, 2 by te volunJe number on vv hi cb t his page resides and a 4 byte unique number. It uses this physical O lD instead oC logical OlDs to avoid the extra d isk I/ 0 needed to t ra nslate a logical OlD to its p hysical location. Since OIDs |
