Blockchain Technology (BT) is a futuristic data management technology that eliminates the intermediary/ third-party/central authority as it is operated over a peer-to-peer network running cryptographic protocols. It is tamper-proof as it utilizes a cryptographic hash feature. Some other features, it offers, are transparency, security, inalterability, immutability, and decentralization; these features of the BTs have acquired the wide attention of the computing research community. While a transaction is occurring between two parties, it ensures that the trust is a consensus-driven built-in technology component instead of relying on a third party for the same. With the help of a consensus algorithm, the newly generated block is appended at the end of the already existing chain. In this paper, a thorough analysis of the various blockchain consensus algorithms is conducted including their benefits and drawbacks. Finally, it enlists the challenges and opportunities in designing blockchain consensus algorithms. Further, it proposes an idea for designing a blockchain consensus algorithm and concludes the discussion.

Location dependent information services (LDIS) can be characterized as the applications that coordinate a cell phone's area or position with other data to give enhanced value of services to the client at right place in the right time from anywhere. In this paper, an algorithm Caching Efficiency with Next Location Prediction Based (CELPB) has been developed that uses a newly developed metric i.e. caching efficiency with next location prediction (CELP) for the computation of valid scope in prediction interval. This metric takes account the future movement behavior of client with the help of Sequential Pattern Mining and Clustering. The mobility rules have also been framed for the prediction of an accurate next location, which can be used in estimating the future movement path (edges) of client if he reached in valid scope area of any data item. Simulation results show that proposed policy achieves up to 10 percent performance improvement compared to earlier cache invalidation policy (CEBAB) for LDIS.

The Two Phase Locking with High Priority (2PL-HP) concurrency control protocol addresses the transaction scheduling issue in a distributed real-time database system (DRTDBS). Although the 2PL-HP protocol is free from priority inversion, it may suffer from the problems such as deadlock, cyclic restart, and starvation of lengthy transactions. In this paper, a Controlled Avoidance of deadlock and starvation causing Resourceful Conflict resolution between Transactions (CART) concurrency control protocol has been proposed to minimize the transactions miss percentage by reducing the wastage of system resources through avoiding the deadlock due to controlled locking and starvation to some extent by ensuring a fairness in the allocation of resources for their completion. DRTDBS is simulated and CART outperforms as compared with previous other protocols.

This paper proposes a new commit protocol for real time distributed database systems, dependency sensitive shadow SWIFT (DSS-SWIFT) protocol where the cohort forks off a replica of itself called a shadow, whenever it borrows dirty value of a data item, and if, the created dependency is abort type as compared to creating shadow in all cases of dependency in shadow PROMPT. Also the health factor of cohort is used for permitting to use dirty value of lender rather than health factor of transaction as whole. The performance of DSS-SWIFT is compared with PROMPT, 2SC and SWIFT protocols for both main memory resident and disk resident databases with and without communication delay. Simulation results show that the proposed protocol improves the system performance up to 7% as transaction miss percentage