| OCR Text |
Show 17 2.5.8 ObjectStore Obj ectStore [14] was de veloped hy Object Design, lnc. It provides a unified programmatic i nt<~Tface to hoth persistent ly a llocated data and transi e ntly a llocated ci<d;a, with object-access speed for pers is tellt data usually equal to that of an inttH't ll ory detef<~Ten c < ' oC a pointer to a t ra nsient data. It provides language interfaces to ( ' a nd C++. Obj ectStore uses virtual addresses as obj ect id e ntifi e rs. It maint a ins a virtual address map which keeps track of t he virtual address corresponding to a database. 'T'htt s , lwo ittdq)('ttdent databases mi ,gh t each use the same address for their own u]I. Jt 'CLS. The acu~ss to pe rs istent objects ts transparent to the use r. ObjcctStore perCol'! lJs a ll virtu a l memory function s fo r tna.pping in-core objects to their physical representation on di sk and vice ve rsa. lt allows the contiguous sto rage of related d<:~.ta e .g ., rnembers of a collection. rnelllbers of a. composite configuration , etc. :\pjJiications can c reate, access, <~.ud ll1 d. llipulate multiple databases at the sa.me time. OhjcctStore allows data to move across cla.ta.bases and objects to refer to oLJjcds in ut ber databases . ObjcctStore supports private and common workspaces. Da.ta. can be checked-out frutn a.nd cbcckecl-·in to tlw common wor kspace. OhjectS tore has two kinds of t ransd. ctions : read-only and ?Lpdatc. lt also supports uestecl transactions. Exception s are JJtuvicled tu lldtidlc tran saction C<lll l-li cls o r a hort s . The locking g ranularity is a pagt· or seg rncn t, su vv lwtJ a persistent clata i t<~m is read , the page or segment on wbi clt it resi des is rea d- locLecl ancl when it is written , the segment is write-locked. It serializes a ll concmTent transactions using the two-phase locking protocol. ObjectS tore s ttpports t b<~ notion of configura tion. A configuration is used to group objects together for p urposes or versioning, lo cking, clustering, etc. It has |
