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Cloud computing is a trend of technology aimed at providing on-demand services with payment based on usage. In order to improve the use of resources, cloud providers adopt multi-tenant approaches, reducing the operation cost of services. Moreover, tenants have irregular workload patterns, which impacts in guarantees of quality of service, mainly due to interference among tenants. This paper proposes PredRep, a predictive approach to characterize the cloud database system workload and automatically provide or reduce resources by replication techniques. In order to evaluate PredRep, some experiments that measure the quality of service and elasticity are presented. Our experiment results confirm that PredRep reduces cost and SLA violations. INTRODUCTIONCloud computing is now a well-established paradigm for the use of computational resources, according to which hardware infrastructure, software, and platforms for the development of new applications are offered as remotely available services on a global scale. 1 Cloud users give up their own computing infrastructure to dispose it through services, based on the pay-as-you-go model, offered by third parties (cloud providers), delegating responsibilities and assuming costs proportionally to the amount of resources used. Cloud providers, in turn, must meet the expected infrastructure needs of their users.The cloud computing adoption makes it an attractive paradigm that is potentially able to meet the most strict quality-of-service (QoS) levels stipulated in a service-level agreement (SLA). However, it is still a challenging issue for providers to efficiently tackle both gradual load variations and load peaks from the workloads, which are highly dynamic and, as such, very unpredictable, 2 in order not to violate SLA requirements to maximize their revenues.Cloud providers adopt the sharing of their computing resources among users, thus optimizing resource usage, reducing costs, and maximizing profits. There are several levels of resource sharing that define the granule shared for the different users of the cloud. For this, there is the multi-tenancy, which is a technique used to consolidate multiple tenants in a computational resource. 3 In the cloud database context, a tenant can be a tuple, table, database, DBMS, OS, or VM. For each tenant type, there is a multi-tenant model associated. However, the shared DBMS multi-tenant model has been the most widely adopted in the database management platforms. 4 In this model, a DBMS manages multiple tenants where a tenant is a database.Dynamic provisioning techniques are designed to handle irregular workloads, so that SLA violations and their contractual penalties associated are avoided or limited, reducing costs from the cloud provider perspective. 4 These techniques usually take action based on workload observation and can be classified as either reactive or proactive. Proactive solutions apply sophisticated system models for prediction 2 and use forecast results to triggering allocations of expected need in advance. In contrast,...

Cloud computing is a trend of technology aimed at providing on-demand services with payment based on usage. To improve the use of resources, cloud providers adopt multi-tenant approaches, reducing the operation cost of services. Moreover, tenants have irregular workload patterns, impacting in the guarantees of quality of service, mainly due to interference between tenants. This paper proposes an approach to improve quality of service for multi-tenant RDBMS. This approach employs migration techniques of tenants, system monitoring, allocation strategy, forecast approach, and benefits of cloud infrastructure to improve performance and reduce provider cost. We carried out experiments on performance and resource usage in order to evaluate it.

We show that the definition of the city boundaries can have a dramatic influence on the scaling behavior of the night-time light (NTL) as a function of population (POP) in the US. Precisely, our results show that the arbitrary geopolitical definition based on the Metropolitan/Consolidated Metropolitan Statistical Areas (MSA/CMSA) leads to a sublinear power-law growth of NTL with POP. On the other hand, when cities are defined according to a more natural agglomeration criteria, namely, the City Clustering Algorithm (CCA), an isometric relation emerges between NTL and population. This discrepancy is compatible with results from previous works showing that the scaling behaviors of various urban indicators with population can be substantially different for distinct definitions of city boundaries. Moreover, considering the CCA definition as more adequate than the MSA/CMSA one because the former does not violate the expected extensivity between land population and area of their generated clusters, we conclude that, without loss of generality, the CCA measures of light pollution and population could be interchangeably utilized in future studies

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In this paper we present an algorithm for optimal processing of time-dependent sequenced route queries in road networks, i.e., given a road network where the travel time over an edge is time-dependent and a given ordered list of categories of interest, we find the fastest route between an origin and destination that passes through a sequence of points of interest belonging to each of the specified categories of interest. For instance, considering a city road network at a given departure time, one can find the fastest route between one's work and his/her home, passing through a bank, a supermarket and a restaurant, in this order. The main contribution of our work is the consideration of the time-dependency of the network, a realistic characteristic of urban road networks, which has not been considered previously when addressing the optimal sequenced route query. Our approach uses the A* search paradigm that is equipped with an admissible heuristic function, thus guaranteed to yield the optimal solution, along with a pruning scheme for further reducing the search space. In order to compare our proposal we extended a previously proposed solution aimed at non-time dependent sequenced route queries, enabling it to deal with the timedependency. Our experiments using real and synthetic data sets have shown our proposed solution to be up to two orders of magnitude faster than the temporally extended previous solution.