A survey of checkpointing algorithms for parallel and distributed computers

Checkpoint is defined as a designated place in a program at which normal processing is interrupted specifically to preserve the status information necessary to allow resumption of processing at a later time. Checkpointing is the process of saving the status information. This paper surveys the algorithms which have been reported in the literature for checkpointing parallel/distributed systems. It has been observed that most of the algorithms published for checkpointing in message passing systems are based on the seminal article by Chandy and Lamport. A large number of articles have been published in this area by relaxing the assumptions made in this paper and by extending it to minimise the overheads of coordination and context saving. Checkpointing for shared memory systems primarily extend cache coherence protocols to maintain a consistent memory. All of them assume that the main memory is safe for storing the context. Recently algorithms have been published for distributed shared memory systems, which extend the cache coherence protocols used in shared memory systems. They however also include methods for storing the status of distributed memory in stable storage. Most of the algorithms assume that there is no knowledge about the programs being executed. It is however felt that in development of parallel programs the user has to do a fair amount of work in distributing tasks and this information can be effectively used to simplify checkpointing and rollback recovery

Priority-based speculative locking protocols for distributed real-time database systems.

With globalization, multinational networked organizations' need for exchange of information has led to the emergence of applications that are heavily dependent on globally distributed and constantly changing data. Such applications include, stock trading, Computer Aided Design and Manufacturing (CAD/CAM), online reservation systems, telecommunication systems, e-commerce systems and real time navigation systems. These applications introduce the need for distributed real time database systems (DRTDBS) which must access/manipulate data spread over a network in addition to meeting the real time constraints and maintaining database consistency. In order to improve performance within DRTDBS, attention needs to be given to concurrency control mechanism and transaction's time constraints. A number of protocols have been suggested in recent years to address these issues. One of the proposed protocols, Speculative Locking (SL), has especially demonstrated the capability of improving performance within Distributed Database System by allowing parallelism between conflicting transactions without violating serializability. This research extends SL by giving it the capability of taking a transaction's priority into consideration when scheduling transactions. In addition, a nested transaction model is used to access the data that is distributed across the network. We propose two new Priority-based Speculative Locking protocols: (1) Preemptive Speculative Locking (PSL) and (2) Priority inheritance Speculative Locking (PiSL). PSL extends SL by allowing any incoming higher priority transaction to preempt and abort any lower priority transaction in case of lock conflict thus giving the higher priority transaction a chance to meet the deadline. PiSL, on the other hand, attempts to prevent any wasted work by avoiding preemption by a higher priority transaction. Instead, the lower priority transaction inherits the priority of the blocked transaction. This gives both transactions an opportunity to meet their deadline whenever possible.The original print copy of this thesis may be available here: http://wizard.unbc.ca/record=b159863

Database recovery

Recovery techniques are an important aspect of database systems. They are essential to ensure that data integrity is maintained after any type of failure occurs. The recovery mechanism must be designed so that the availability and performance of the system are not unacceptably impacted by the recovery algorithms running during normal execution. On the other hand, enough information must be stored so that the database can be restored or transactions backed out in a reasonable amount of time. Concepts, techniques, and problems associated with database recovery will be presented in this thesis. The recovery issues for both centralized and distributed systems will be discussed, along with the tradeoffs of different recovery tools. The database recovery schemes in IMS/VS, DB2 and SDD-1 will be described to show approaches in existing systems

A Survey on Transactional Stream Processing

Transactional stream processing (TSP) strives to create a cohesive model that merges the advantages of both transactional and stream-oriented guarantees. Over the past decade, numerous endeavors have contributed to the evolution of TSP solutions, uncovering similarities and distinctions among them. Despite these advances, a universally accepted standard approach for integrating transactional functionality with stream processing remains to be established. Existing TSP solutions predominantly concentrate on specific application characteristics and involve complex design trade-offs. This survey intends to introduce TSP and present our perspective on its future progression. Our primary goals are twofold: to provide insights into the diverse TSP requirements and methodologies, and to inspire the design and development of groundbreaking TSP systems