12 research outputs found

    A comparative study of transaction management services in multidatabase heterogeneous systems

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    Multidatabases are being actively researched as a relatively new area in which many aspects are not yet fully understood. This area of transaction management in multidatabase systems still has many unresolved problems. The problem areas which this dissertation addresses are classification of multidatabase systems, global concurrency control, correctness criterion in a multidatabase environment, global deadlock detection, atomic commitment and crash recovery. A core group of research addressing these problems was identified and studied. The dissertation contributes to the multidatabase transaction management topic by introducing an alternative classification method for such multiple database systems; assessing existing research into transaction management schemes and based on this assessment, proposes a transaction processing model founded on the optimal properties of transaction management identified during the course of this research.ComputingM. Sc. (Computer Science

    An Agent Based Transaction Manager for Multidatabase Systems

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    A multidatabase system (MDBMS) is a facility that allows users to access data located in multiple autonomous database management systems (DBMSs) at different sites. To ensure global atomicity for multidatabase transactions, a reliable global atomic commitment protocol is a possible solution. In this protocol a centralized transaction manager (TM) receives global transactions, submits subtransactions to the appropriate sites via AGENTS. An AGENT is a component of MDBS that runs on each site; AGENTS after receiving subtransactions from the transaction manager perform the transaction and send the results back to TM. We have presented a unique proof-of-concept, a JAVA application for an Agent Based Transaction Manager that preserves global atomicity. It provides a user friendly interface through which reliable atomic commitment protocol for global transaction execution in multidatabase environment can be visualized. We demonstrated with three different test case scenarios how the protocol works. This is useful in further research in this area where atomicity of transactions can be verified for protocol correctness

    New Protocol for Multidatabase Concurrency Control

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    Towards interoperability in heterogeneous database systems

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    Distributed heterogeneous databases consist of systems which differ physically and logically, containing different data models and data manipulation languages. Although these databases are independently created and administered they must cooperate and interoperate. Users need to access and manipulate data from several databases and applications may require data from a wide variety of independent databases. Therefore, a new system architecture is required to manipulate and manage distinct and multiple databases, in a transparent way, while preserving their autonomy. This report contains an extensive survey on heterogeneous databases, analysing and comparing the different aspects, concepts and approaches related to the topic. It introduces an architecture to support interoperability among heterogeneous database systems. The architecture avoids the use of a centralised structure to assist in the different phases of the interoperability process. It aims to support scalability, and to assure privacy and nfidentiality of the data. The proposed architecture allows the databases to decide when to participate in the system, what type of data to share and with which other databases, thereby preserving their autonomy. The report also describes an approach to information discovery in the proposed architecture, without using any centralised structure as repositories and dictionaries, and broadcasting to all databases. It attempts to reduce the number of databases searched and to preserve the privacy of the shared data. The main idea is to visit a database that either containsthe requested data or knows about another database that possible contains this data

    Global scheduling for flexible transactions in heterogeneous distributed database systems

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    A Framework for Flexible Transaction Management in Multidatabase Systems

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    Supporting Altruistic Protocol in Multidatabase System

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    Computer Science

    Distributed Transactions using the SAGA pattern

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    Οι κατανεμημένες συναλλαγές αποτελούν κρίσιμο συστατικό των σύγχρονων κατανεμημένων συστημάτων, καθώς εξασφαλίζουν τη συνοχή και την ακεραιότητα των δεδομένων σε πολλαπλές βάσεις δεδομένων, διακομιστές ή υπηρεσίες. Είναι ιδιαίτερα σημαντικές στα σύγχρονα κατανεμημένα συστήματα, τα οποία είναι συχνά πολύπλοκα, δυναμικά με πολλά διασυνδεδεμένα στοιχεία, καθώς και σε συστήματα που περιλαμβάνουν ευαίσθητα ή κρίσιμα δεδομένα. Χωρίς κατανεμημένες συναλλαγές, θα ήταν δύσκολο να διασφαλιστεί ότι τα δεδομένα ενημερώνονται με συνέπεια και ορθότητα σε πολλαπλά συστήματα, γεγονός που θα μπορούσε να οδηγήσει σε ασυνέπειες και απώλεια δεδομένων. Ο στόχος μιας κατανεμημένης συναλλαγής είναι να διασφαλίσει ότι όλες οι λειτουργίες είτε όλες δεσμεύονται και τίθενται σε ισχύ είτε όλες ανακαλούνται και δεν έχουν κανένα αποτέλεσμα, ακόμη και σε περίπτωση αποτυχιών ή σφαλμάτων. Ωστόσο, οι παραδοσιακές προσεγγίσεις για την υλοποίηση κατανεμημένων συναλλαγών, όπως το Two-Phase Commit protocol (2PC), μπορεί να είναι πολύπλοκες και επιρρεπείς σε σφάλματα. Το πρότυπο SAGA είναι μια πολλά υποσχόμενη εναλλακτική προσέγγιση για την υλοποίηση κατανεμημένων συναλλαγών, καθώς επιτρέπει μεγαλύτερη ευελιξία και ανθεκτικότητα στα κατανεμημένα συστήματα. Σε ένα SAGA, κάθε βήμα αντιμετωπίζεται ως ξεχωριστή συναλλαγή, και εάν κάποιο βήμα αποτύχει, η διαδικασία ανατρέπεται σε μια προηγούμενη γνωστή καλή κατάσταση και ενεργοποιείται μια διαδικασία χειρισμού σφαλμάτων. Αυτό επιτρέπει τη μερική αποτυχία και τη δυνατότητα ανάκαμψης από αυτήν, καθιστώντας το πρότυπο SAGA ιδιαίτερα κατάλληλο για χρήση σε σύγχρονα κατανεμημένα συστήματα. Σε αυτή τη διπλωματική εργασία, θα διερευνήσουμε τη χρήση του προτύπου Saga για την υλοποίηση κατανεμημένων συναλλαγών σε κατανεμημένα συστήματα. Θα ξεκινήσουμε παρέχοντας μια επισκόπηση των κατανεμημένων συναλλαγών και των προκλήσεων που θέτουν στα σύγχρονα κατανεμημένα συστήματα. Στη συνέχεια θα παρουσιάσουμε το πρότυπο SAGA και θα συζητήσουμε τα οφέλη και τις προκλήσεις του. Αμέσως μετά, θα παρουσιάσουμε μια μελέτη περίπτωσης που υλοποιεί την «orchestrated» προσέγγισή μας - piSaga - για κατανεμημένες συναλλαγές σε Spring Boot microservices και θα πραγματοποιήσουμε ορισμένα πειράματα προκειμένου να μετρήσουμε την απόδοσή της σε σχέση με μια «choreographed» λύση. Τέλος, θα καταλήξουμε συνοψίζοντας τις βασικές ιδέες και τις συνεισφορές της ανάλυσής μας.Distributed transactions are a crucial component of modern distributed systems, as they ensure data consistency and integrity across multiple databases, servers, or services. They are essential in modern distributed systems, which are often complex and dynamic environments with many interconnected components, and in systems that involve sensitive or critical data. Without distributed transactions, ensuring that data is consistently and correctly updated across multiple systems would be challenging, which could lead to inconsistencies and data loss. The goal of a distributed transaction is to ensure that all operations either commit and take effect or roll back and have no effect, even in the case of failures or errors. However, traditional approaches to implementing distributed transactions, such as the Two-Phase commit (2PC) protocol, can be inflexible and prone to failure in complex and dynamic environments. The SAGA pattern is a promising alternative approach to implementing distributed transactions, as it allows for more flexibility and resilience in distributed systems. In a SAGA, each step in a long-running business process is treated as a separate transaction, and if any step fails, the process is rolled back to a previously known good state, and an error-handling process is triggered. This allows for partial failures and the ability to recover from them, making the SAGA pattern particularly well-suited for use in modern distributed systems. In this thesis, we will explore the use of the SAGA pattern for implementing distributed transactions in distributed systems. We will begin by providing an overview of distributed transactions and their challenges in modern distributed systems. We will then introduce the SAGA pattern and discuss its benefits and challenges. Next, we will present a case study that implements our orchestrated approach - piSaga - for distributed transactions in Spring Boot microservices. We will also conduct experiments to measure its performance against a choreographed solution. Finally, we will summarize the key insights and contributions of our analysis

    An evaluation of methodological issues in workflow management

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    Ankara : Department of Computer Engineering and Information Science and the Institute of Engineering and Science of Bilkent University, 1998.Thesis (Master's) -- Bilkent University, 1998.Includes bibliographical references leaves 75-79.Sotnikova, AnastasiaM.S

    Combining SOA and BPM Technologies for Cross-System Process Automation

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    This paper summarizes the results of an industry case study that introduced a cross-system business process automation solution based on a combination of SOA and BPM standard technologies (i.e., BPMN, BPEL, WSDL). Besides discussing major weaknesses of the existing, custom-built, solution and comparing them against experiences with the developed prototype, the paper presents a course of action for transforming the current solution into the proposed solution. This includes a general approach, consisting of four distinct steps, as well as specific action items that are to be performed for every step. The discussion also covers language and tool support and challenges arising from the transformation
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