Using Tickets to Enforce the Serializability of Multidatabase Transactions

Wright State University CORE Scholar The Ohio Center of Excellence in Knowledge- Kno.e.sis Publications Enabled Computing (Kno.e.sis) 2-1994 Using Tickets to Enforce the Serializability of Multidatabase Transactions Dimitrios Georgakopoulos Marek Rusinkiewicz Amit P. Sheth Wright State University - Main Campus, [email protected] Follow this and additional works at: https://corescholar.libraries.wright.edu/knoesis Part of the Bioinformatics Commons, Communication Technology and New Media Commons, Databases and Information Systems Commons, OS and Networks Commons, and the Science and Technology Studies Commons Repository Citation Georgakopoulos, D., Rusinkiewicz, M., & Sheth, A. P. (1994). Using Tickets to Enforce the Serializability of Multidatabase Transactions. IEEE Transactions on Knowledge and Data Engineering, 6 (1), 166-180. https://corescholar.libraries.wright.edu/knoesis/823 This Article is brought to you for free and open access by the The Ohio Center of Excellence in Knowledge-Enabled Computing (Kno.e.sis) at CORE Scholar. It has been accepted for inclusion in Kno.e.sis Publications by an authorized administrator of CORE Scholar. For more information, please contact [email protected]. IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING VOL XX NO Y DECEMBER Using Tickets to Enforce the Serializabil ity of Multidatabase Transactions Dimitrios Georgakop oulos Marek Rusinkiewicz and Amit Sheth Abstract To enforce global serializabilityinamulti global transaction database environmentthemultidatabase transaction man G ager must takeinto account the indirect transitive con icts b etween multidatabase transactions caused bylocal transactions Such conicts are dicult to resolve b ecause MDBS local transaction local transaction the b ehavior or even the existence of lo cal transactions is P P not known to the multidatabase system Toovercome these P P g g g k diculties we prop ose to incorp orate additional data ma P T T k P P nipulation op erations in the subtransactions of eachmul P P Pq tidatabase transaction We show that if these op erations create direct conicts b etween subtransactions at each par LDBS LDBS LDBS k ticipating lo cal database system indirect conicts can b e resolved even if the multidatabase system is not aware of their existence Based on this approach weintro duce opti data data data mistic and conservativemultidatabase transaction manage base base base ment metho ds that require the lo cal database systems to assure only lo cal serializability The prop osed metho ds do not violate the autonomy of the lo cal database systems and guarantee global serializabilitybypreventing multidatabase transactions from b eing serialized in dierentways at the participating database systems Renements of these meth Fig Multidatabase system architecture o ds are also prop osed for multidatabase environments where the participating database systems allowschedules that are cascadeless or transactions have analogous execution and se rialization orders In particular weshow that forced lo cal systems havetosolve transaction managementmecha conicts can b e eliminated in rigorous lo cal systems lo cal nisms in MDBSs must also cop e with heterogeneity and cascadelessness simplies the design of a global scheduler autonomy of the participating LDBSs and that lo cal strictness oers no signicantadvantages over cascadelessness The most imp ortant heterogeneities from the p ersp ec Keywords multidatabase transactions serializabilityin tive of transaction management are dissimilarities in i direct conicts tickets analogous execution and serializa the transaction management primitives and related error tion orders rigorous scheduling detection facilities available through the LDBS interfaces and ii the concurrency control commitment and recov I Introduction ery schemes used by the LDBSs Lo cal autonomy is the most fundamental assumption of ULTIDATABASE SYSTEM MDBS is a fa the MDBS concept Autonomy sp ecies the degree of in cility that supp orts global applications accessing M dep endence and control the LDBSs haveover their data data stored in multiple databases It is assumed that the Since total autonomy means lack of co op eration and com access to these databases is controlled by autonomous and munication and hence total isolation some less extreme p ossibly heterogeneous Local Database Systems LDBSs notions of LDBS autonomyhave b een prop osed in the lit The MDBS architecture Figure allows local transac erature GarciaMolina and Kogan ex tions and global transactions to co exist Lo cal transac plored the concept of no de site autonomy in the con tions are submitted directly to a single LDBS while the text of a distributed system Veijalainen classies the multidatabase global transactions are channeled through LDBS autonomy requirementinto design autonomy execu the MDBS interface The ob jectives of a multidatabase tion autonomy and communication autonomy In addition transaction management are to avoid inconsistent retrievals to these notions of autonomy Sheth and Larson identify and to preserve the global consistency in the presence of additional LDBS prop erties that preserve asso ciation au multidatabase up dates These ob jectives are more di tonomy In this pap er we consider that LDBS autonomy cult to achieve in MDBSs than in homogeneous distributed is not violated if the following two conditions are satised database systems b ecause in addition to the problems The LDBS is not mo died in anyway caused by data distribution that all distributed database The lo cal transactions submitted to the LDBS need not to b e mo died in anyway eg to takeinto ac D Georgakop oulos is with the Distributed Ob ject Computing De partment GTE Lab oratories Incorp orated Sylvan Road MS count that the LDBS participates in a MDBS Waltham MA Inamultidatabase environment the serializability of lo M Rusinkiewicz is with the Department of Computer Science Uni cal schedules is by itself not sucient to maintain multi versity of Houston Houston TX A Sheth is with Bellcore Ho es Lane PiscatawayNJ database consistencyTo ensure that global serializability IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING VOL XX NO Y DECEMBER cal database management systems are discussed in Section is not violated lo cal schedules must b e validated bythe III In Section IV weintro duce the concept of a ticket MDBS However the lo cal serialization orders are neither and prop ose the Optimistic Ticket Method OTM for mul rep orted by the lo cal database systems nor can they b e tidatabase transaction management To guarantee global determined by controlling the submission of global sub serializability OTM requires that the LDBSs ensure lo cal transactions or observing their execution order To deter serializability In Section V weintro duce the Conservative mine the serialization order of the global transactions at Ticket Method CTM that also requires global transac each LDBS the MDBS must deal not only with direct con tions to taketickets but is free from global restarts Varia icts that may exist b etween the subtransactions of multi tions of OTM and CTM that use simpler global schedulers database transactions but also with the indirect conicts but work only in multidatabase systems in which all lo cal that may b e caused by lo cal transactions Since the MDBS systems are cascadeless are presented in Section VI In has no information ab out the existence and b ehavior of lo Section VI I weintro duce the concept of implicit tickets cal transactions determining if an execution of global and and prop ose the Implicit Ticket Method ITM whichdoes lo cal transactions is globally serializable is dicult An not require subtransaction tickets but works only in multi example illustrating this problem is presented in the next database environments where the participating LDBSs are section rigorous Integrating the metho ds ab ove in mixed multi Several solutions have b een prop osed in the literature database schedulers is discussed in Section VI I I Finally to deal with this problem however most of them are not in Section IX we summarize our results satisfactory The main problem with the ma jorityofthe prop osed solutions is that they do not provide a wayofas II Problems in maintaining global suring that the op eration execution order of global trans serializability and related work actions which can b e controlled by the MDBS is reected in the lo cal serialization order of the global transactions Many algorithms that have b een prop osed for transac pro duced by the LDBSs For example it is p ossible that a tion management in distributed systems are not directly global transaction G is executed and committed at some i applicable in MDBSs b ecause of the p ossibility of indirect LDBS b efore another global transaction G but their lo j conicts caused by the lo cal transactions To illustrate this cal serialization order is reversed In this pap er we address point consider Figure which depicts the execution of two this problem byintro ducing a technique that disallows such multidatabase transactions G and G and a lo cal trans lo cal schedules and enables the MDBS to determine the se action T If a transaction G reads a data item awe draw i rialization order of global transactions in each participating an arc from a to G An arc from G to a denotes that i i LDBS Our metho d do es not violate the lo cal autonomy G writes a In our example the global transactions have i and is applicable to all LDBSs that ensure lo cal serializ subtransactions in b

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