Cache Consistency Maintenance Research Articles

Performance Analysis of Cache Consistency Maintenance in Mobile Environment using Agent Technique

This paper illustrates three Agents Based Techniques namely, Thread Based Cache Consistency Model, Multiple Server Cache Consistency Model, and Cluster Based Cache Consistency Models used to solve the problems of cache consistency maintenance and also compared with existing method. The drawbacks of existing method are latency, excessive bandwidth wastage, query delay, server overloads as well as network traffic. In the Thread Based Cache Consistency Model, the log is maintained in both server and client, it is easy for server as well as client to make their data object reliable. Agents at server and client make an internal request response operation(s) to access or update data object. It is easy to update the cached data and as well to maintain consistency between client and server. The Multiple Server Cache Consistency Models where the node is designed as a middle server (master client cache) between server and clients, some of the client data cache is placed in a middle server. The middle server is near the client, as result the communication cost and energy consumption is comparatively less. It reduces server’s workload. The Cluster Based Cache Consistency Model designed as a Cluster head node between the server and the client using agent technique, effectively reduces the query latency. These three Agent Based Models are implemented in Ns2 and their performance was analysed and compared with existing method. Agent Based Technique resulted in better performance in relation to update delay, through various numbers of nodes and update rate.

Performance Analysis of Cache Consistency Maintenance in Mobile Environment using Agent Technique

This paper illustrates three Agents Based Techniques namely, Thread Based Cache Consistency Model, Multiple Server Cache Consistency Model, and Cluster Based Cache Consistency Models used to solve the problems of cache consistency maintenance and also compared with existing method. The drawbacks of existing method are latency, excessive bandwidth wastage, query delay, server overloads as well as network traffic. In the Thread Based Cache Consistency Model, the log is maintained in both server and client, it is easy for server as well as client to make their data object reliable. Agents at server and client make an internal request response operation(s) to access or update data object. It is easy to update the cached data and as well to maintain consistency between client and server. The Multiple Server Cache Consistency Models where the node is designed as a middle server (master client cache) between server and clients, some of the client data cache is placed in a middle server. The middle server is near the client, as result the communication cost and energy consumption is comparatively less. It reduces server’s workload. The Cluster Based Cache Consistency Model designed as a Cluster head node between the server and the client using agent technique, effectively reduces the query latency. These three Agent Based Models are implemented in Ns2 and their performance was analysed and compared with existing method. Agent Based Technique resulted in better performance in relation to update delay, through various numbers of nodes and update rate.

SDCI: SCALABLE DISTRIBUTED CACHE INDEXING FOR CACHE CONSISTENCY FOR MOBILE ENVIRONMENTS

In this paper, we suggest a new cache consistency maintenance scheme, namely Scalable distributed cache indexing for Cache Consistency (SDCI), for mobile environments. It mainly depends on 3 key features. They are: (1) Utilization of standard bits at server and Mobile Node's cache for maintaining cache consistency; (2) Utilization of Local Cache Standard (LC-standard) for all entries in Mobile Node's cache after its invalidation for maximizing the broadcast bandwidth efficiency; (3) Making every valid entry of Mobile Node's cache to whenever it wakes up. These features make the SDCI a good scalable algorithm with minimum database management overhead. By observing Comprehensive simulation results we can see that the performance of SDCI is superior to those of existing algorithms.

Cluster Based Data Consistency for Cooperative Caching over Partitionable Mobile Adhoc Network

Problem statement: Data availability and consistency are foremost issues in Mobile Ad hoc Networks due to the absence of permanent infrastructure. Cooperative caching addresses the data availability issue through coordinating the mobile nodes and sharing the cache copies among them. In the meantime, the mobile node must ensure the staleness of cache copies. The consistency maintenance resolves the staleness of the data among the source and caching node. Due to addition of more mobile nodes the network size is increased and it leads to increase the caching nodes. The mobility and disconnections causes additional overhead, latency and reduces the data delivery success ratio while updating the cache copy from the source. Approach: This study proposed Adaptive Push and Pull Algorithm for Clusters (APPC) and Cluster Based Data Consistency (CBDC) approach to address the consistency requirements and maintenance in mobile ad hoc network. Results: The CBDC satisfy the consistency requirements in partitioned clusters. The source node transmits the updated data through the cluster heads to the caching nodes. The APPC ensures the validity of cache copy by threshold Time-to-Live (TTL). Thus it provides efficient valid data accessibility in mobile ad hoc network. Conclusion: The simulation results shown that this proposed approach increases packet success ratio and reduces the delay and overhead when compared with the existing approaches Flexible Cache Consistency (FCPP) maintenance and Cluster Based Cooperative Caching Technique (CBCCT) for increasing number of nodes and speed respectively.

A Multi-Level Cache Approach for Realtime Visualization of Massive 3D GIS Data

The real-time visualization of 3D GIS at a whole city scale always faces the challenge of dynamic data loading with high-efficiency. Based on the multi-tier distributed 3D GIS framework, this paper presents a multi-level cache approach for dynamic data loading. It aims to establish in 3D GIS spatial database engine (3DGIS-SDE) the unified management mechanism of caches on three levels, including: the client memory cache (CMC) oriented to sharing application, the client file cache (CFC) organized by index, as well as the application server memory cache (ASMC) of structural consistency. With the help of the proposed optimized cache replacement policy, multi-level cache consistency maintenance as well as multithread loading model designed in the paper, the engine is able to adaptively make full use of each-level caches according to their own application properties and achieve effective coordination between them. Finally, a practical 3D GIS database based on Oracle 11g is employed for test. The experimental results prove this approach could satisfy multi-user concurrent applications of 3D visual exploration.

Mitigating channel usage in cooperative caching for Mobile Ad hoc Networks

Cooperative caching supports efficient data dissemination and sharing in Mobile Ad hoc Networks (MANETs). Existing cache consistency maintenance algorithms are stateless, where the data source node is unaware of the cache node status. The stateless algorithm is cost-effective as it does not maintain status and suffers from paying to broadcasting. Stateful algorithms can significantly reduce the consistency maintenance cost by maintaining status of the cached data and selectively propagating the data updates. In this paper, a stateful cache consistency maintenance algorithm, Selective Push and Pull (SPP) is proposed which improves the performance of the MANET by saving the bandwidth and reducing the query delay. Omega Consistency Model is designed to satisfy the user specified consistency.

Flexible Cache Consistency Maintenance over Wireless Ad Hoc Networks

One of the major applications of wireless ad hoc networks is to extend the Internet coverage and support pervasive and efficient data dissemination and sharing. To reduce data access cost and delay, caching has been widely used as an important technique. The efficiency of data access in caching systems largely depends on the cost for maintaining cache consistency, which can be high in wireless ad hoc networks due to network dynamism. Therefore, to make better trade-off between cache consistency and the cost incurred, it would be highly desirable to provide users the flexibility in specifying consistency requirements for their applications. In this paper, we propose a general consistency model called Probabilistic Delta Consistency (PDC), which integrates the flexibility granted by existing consistency models, covering them as special cases. We also propose the Flexible Combination of Push and Pull (FCPP) algorithm which satisfies user-specified consistency requirements under the PDC model. The analytical model of FCPP is used to derive the balance of minimizing the consistency maintenance cost and ensuring the specified consistency requirement. Extensive simulations are conducted to evaluate whether FCPP can satisfy arbitrarily specified consistency requirements, and whether FCPP works cost-effectively in dynamic wireless ad hoc networks. The evaluation results show that FCPP can adaptively tune itself to satisfy various user-specified consistency requirements. Moreover, it can save the traffic cost by up to 50 percent and reduce the query delay by up to 40 percent, compared with the widely used Pull with TTR algorithm.

Cooperative cache consistency maintenance for pervasive internet access

AbstractCooperative caching is an important technique to support pervasive Internet access. In order to ensure valid data access, the cache consistency must be maintained properly. However, this problem has not been sufficiently studied in mobile computing environments, especially those with ad hoc networks. There are two essential issues in cache consistency maintenance: consistency control initiation and data update propagation. Consistency control initiation not only decides the cache consistency provided to the users, but also impacts the consistency maintenance cost. This issue becomes more challenging in asynchronous and fully distributed ad hoc networks. To this end, we propose the predictive consistency control initiation (PCCI) algorithm, which adaptively initiates consistency control based on its online predictions of forthcoming data updates and cache queries. In order to efficiently propagate data updates through multi‐hop wireless connections, the hierarchical data update propagation (HDUP) algorithm is proposed. Theoretical analysis shows that cooperation among the caching nodes facilitates data update propagation. Extensive simulations are conducted to evaluate performance of both PCCI and HDUP. Evaluation results show that PCCI cost‐effectively initiates consistency control even when faced with dynamic changes in data update rate, cache query rate, node speed, and number of caching nodes. The evaluation results also show that HDUP saves cost for data update propagation by up to 66%. Copyright © 2009 John Wiley & Sons, Ltd.

Semantic-Aware and QoS-Aware Image Caching in Ad Hoc Networks

Semantic caching was originally used for structural data objects such as 2D location data and cannot be directly applied to mobile image data access. First, traditional semantic caching relies on exact match and therefore is not suitable for approximate and similarity-based queries. Second, the semantic description of cached data is defined on query context instead of data content, which leads to inefficient use of cache storage. Third, the semantic description of cached data does not reflect the popularity of the data, making it difficult to conduct popularity-driven content analysis and prediction. To facilitate content-based image retrieval in wireless ad hoc networks, we propose a semantic-aware image caching (SAIC) scheme in this paper. The proposed scheme can efficiently utilize the cache space and significantly reduce the cost of image retrieval. The proposed SAIC scheme is based on several innovative ideas: 1) multilevel representation of the semantic contents, 2) association-based and Bayesian probability-based content prediction, 3) constraint-based representation method showing the semantic similarity between images, 4) nonflooding query processing, and 5) adaptive cache consistency maintenance. The proposed model is introduced, and through extensive simulation, its behavior has been compared against two state-of-the-art ad hoc caching schemes as advanced in the literature.

Dynamic cache consistency schemes for wireless cellular networks

Caching frequently accessed data objects at the local buffer of a mobile user (MU) has been found to be very effective in improving information availability in mobile wireless environments. Several mechanisms have been proposed in the literature to address the challenging problem of cache consistency in cellular wireless networks. However, these mechanisms are limited to single cell systems. In this paper, we develop a novel Dynamic Scalable Asynchronous Cache Consistency Scheme (DSACCS) that can adaptively maintain mobile data objects globally or locally depending on the minimum consistency maintenance cost in multi-cell systems. The cost function is derived by taking into account each data object's update frequency, MUs' access pattern and roaming frequency, number of cells and number of MUs in the system. Extensive simulation studies demonstrate that DSACCS outperforms three existing cache strategies extended to multi-cell environments. The three cache consistency strategies are homogeneous invalidation reports (IRs), inhomogeneous IR without roaming check, and inhomogeneous IR with roaming check. Finally, an improvisation of DSACCS, called DSACCS-G, is proposed for grouping cells in order to facilitate effective cache consistency maintenance in multi-cell systems.

Deferred locking with shadow transaction for client–server DBMSs

Data-shipping systems that allow inter-transaction caching raise the need of a transactional cache consistency maintenance ( CCM ) protocol because each client is able to cache a portion of the database dynamically. Deferred locking ( DL ) is a new CCM scheme that is capable of reducing the communication overhead required for cache consistency checking. Due to its low communication overhead, DL could show a superior performance, but it tends to exhibit a high ratio of transaction abort. To cope with this drawback, we develop a new notion of shadow transaction, which is a backup-purpose one that is kept ready to replace an aborted transaction. This notion and the locking mechanism of DL have been incorporated into deferred locking with shadow transaction. Using a distributed database simulation model, we evaluate the performance of the proposed schemes under a wide range of workloads.

A Scalable Asynchronous Cache Consistency Scheme (SACCS) for mobile environments

In the literature, there exit two types of cache consistency maintenance algorithms for mobile computing environments: stateless and stateful. In a stateless approach, the server is unaware of the cache contents at a mobile user (MU). Even though stateless approaches employ simple database management schemes, they lack scalability and ability to support user disconnectedness and mobility. On the other hand, a stateful approach is scalable for large database systems at the cost of nontrivial overhead due to server database management. We propose a novel algorithm, called Scalable Asynchronous Cache Consistency Scheme (SACCS), which inherits the positive features of both stateless and stateful approaches. SACCS provides a weak cache consistency for unreliable communication (e.g., wireless mobile) environments with small stale cache hit probability. It is also a highly scalable algorithm with minimum database management overhead. The properties are accomplished through the use of flag bits at the server cache (SC) and MU cache (MUC), an identifier (ID) in MUC for each entry after its invalidation, and estimated time-to-live (TTL) for each cached entry, as well as rendering of all valid entries of MUC to uncertain state when an MU wakes up. The stale cache hit probability is analyzed and also simulated under the Rayleigh fading model of error-prone wireless channels. Comprehensive simulation results show that the performance of SACCS is superior to those of other existing stateful and stateless algorithms in both single and multicell mobile environments.

Transactional client-server cache consistency

Client-server database systems based on a data shipping model can exploit client memory resources by caching copies of data items across transaction boundaries. Caching reduces the need to obtain data from servers or other sites on the network. In order to ensure that such caching does not result in the violation of transaction semantics, a transactional cache consistency maintenance algorithm is required. Many such algorithms have been proposed in the literature and, as all provide the same functionality, performance is a primary concern in choosing among them. In this article we present a taxonomy that describes the design space for transactional cache consistency maintenance algorithms and show how proposed algorithms relate to one another. We then investigate the performance of six of these algorithms, and use these results to examine the tradeoffs inherent in the design choices identified in the taxonomy. The results show that the interactions among dimensions of the design space impact performance in many ways, and that classifications of algorithms as simply “pessimistic” or “optimistic” do not accurately characterize the similarities and differences among the many possible cache consistency algorithms.