Navathe, Shamkant B.

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Now showing 1 - 4 of 4
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    Minimizing Redundant Work in Lazily Updated Replicated Databases
    (Georgia Institute of Technology, 2000) Omiecinski, Edward ; Navathe, Shamkant B. ; Yee, Wai Gen
    Modern databases which manage lazy (or deferred updates) to clients which subscribe to replicated data do so on a client-by-client basis. They ignore any redundant work done during update processing caused by the commonality in client subscriptions to replicas. This paper proposes a new way to process updates which minimizes this redundancy and results in a reduction of update processing cost at the server in terms of disk space and time consumed in this phase. Ultimately, updates are available quicker, and duration during which clients must enduring stale data is reduced. Results of studies involving, iMobile, a currently available system, are reported, and are extremely encouraging.
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    A Mathematical Optimization Approach To Improve Server Scalability In Intermittently Synchronized Databases
    (Georgia Institute of Technology, 1999) Yee, Wai Gen ; Navathe, Shamkant B. ; Datta, Anindya ; Mitra, Sabyasachi
    This paper addresses a scalability problem in the process of synchronizing the states of multiple client databases which only have deferred access to the server. It turns out that the process of client update file generation is not scalable with the number of clients served. In this paper we concentrate on developing an optimization model to address the scalability problem at the server by aiming for an optimal grouping of data fragments at the server given the "interest sets" of the clients - the set of fragments the client deals with for its"local" processing. The objective is to minimize the total cost of server operation which includes processing updates from all clients and transmission cost of sending the right set of updates to each client based on the client's interest set. An integer programming formulation is developed and solved with an illustrative problem, yielding interesting results.
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    Toward A Method of Grouping Server Data Fragments for Improving Scalability in Intermittently Synchronized Databases
    (Georgia Institute of Technology, 1999) Yee, Wai Gen ; Donahoo, Michael J. ; Navathe, Shamkant B.
    We consider the class of mobile computing applications with periodically connected clients. These clients wish to share data; however, due to the expense of mobile communication, they only connect periodically -- and not necessarily synchronously -- to a common network. Traditionally, a continuously-connected server, containing an aggregate of client data, facilitates sharing amongst clients by allowing the clients to upload local updates and download updates submitted by other clients. The server computes and transmits these updates on a client-by-client basis; consequently, the complexity of these operations is on the order of the number of clients, limiting scalability. Recent research proposes exploiting client data overlap by grouping updates according to how the data is shared amongst clients (data-centric) instead of on a client-by-client basis (client-centric). Each client downloads updates for the relevant set of groups. By grouping, update operation distribution is computed only once per group, irrespective of the number of clients downloading a particular group's updates. Additionally, we may gain bandwidth scalability by employing broadcast delivery since, unlike the case in the per-client approach, multiple clients may be interested in a group's updates. Clearly, group composition directly affects the scalability of this approach. Given a relative cost of resources such as server processing, bandwidth, and storage space, we focus on developing a group derivation approach that significantly improves the scalability of the resources. We construct a formal specification of this problem and discuss the intractability of an optimal solution. Based on observations from the specification, we derive a heuristically based approach and evaluate its efficacy with respect to the client-centric approach. We run experiments on an implemented system that demonstrates that as the amount of overlap increases between client subscriptions, the data-centric approach with groups generated by our heuristic-based algorithm yields significant cost reduction when compared to the traditional client-centric approach.
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    A Greedy Approach For Improving Update Processing In Intermittently Synchronized Databases
    (Georgia Institute of Technology, 1999) Omiecinski, Edward ; Navathe, Shamkant B. ; Ammar, Mostafa H. ; Donahoo, Michael J. ; Malik, Sanjoy ; Yee, Wai Gen
    Replication of data on portable computers is a new DBMS technology aimed at catering to a growing population of mobile database users. Clients can download data items such as email, or sales data from a server onto these machines, per use it during commutes, and return any modifications to the server at the end of the day. In this paper, we describe how the servers in these systems generally process update information for clients and reveal a scalability problem--server processing increases quadratically with respect to increasing numbers of clients. We develop a cost model, and propose a solution based on heuristics. By aggregating client interests into datagroups, based on notions such as interest overlap, we can reduce server cost. These techniques are attractive because they are simple and computationally cheap. Simulations show that even simple techniques may yield significant performance improvements.