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In computer science, multiple granularity locking (MGL) is a locking method used in database management systems (DBMS) and relational databases.
In computer science, a lock or mutex is a synchronization primitive that prevents state from being modified or accessed by multiple threads of execution at once. Locks enforce mutual exclusion concurrency control policies, and with a variety of possible methods there exist multiple unique implementations for different applications.
In databases and transaction processing, two-phase locking (2PL) is a pessimistic concurrency control method that guarantees conflict-serializability. It is also the name of the resulting set of database transaction schedules (histories). The protocol uses locks, applied by a transaction to data, which may block other transactions from accessing the same data during the transaction's life.
Server Message Block (SMB) is a communication protocol used to share files, printers, serial ports, and miscellaneous communications between nodes on a network. On Microsoft Windows, the SMB implementation consists of two vaguely named Windows services: "Server" and "Workstation". It uses NTLM or Kerberos protocols for user authentication. It also provides an authenticated inter-process communication (IPC) mechanism.
Association rule learning is a rule-based machine learning method for discovering interesting relations between variables in large databases. It is intended to identify strong rules discovered in databases using some measures of interestingness. In any given transaction with a variety of items, association rules are meant to discover the rules that determine how or why certain items are connected.
A replay attack is a form of network attack in which valid data transmission is maliciously or fraudulently repeated or delayed. This is carried out either by the originator or by an adversary who intercepts the data and re-transmits it, possibly as part of a spoofing attack by IP packet substitution. This is one of the lower-tier versions of a man-in-the-middle attack. Replay attacks are usually passive in nature.
In real-time computing, priority inheritance is a method for eliminating unbounded priority inversion. Using this programming method, a process scheduling algorithm increases the priority of a process (A) to the maximum priority of any other process waiting for any resource on which A has a resource lock.
A cryptosystem is considered to have information-theoretic security if the system is secure against adversaries with unlimited computing resources and time. In contrast, a system which depends on the computational cost of cryptanalysis to be secure is called computationally, or conditionally, secure.
Click fraud is a type of fraud that occurs on the Internet in pay per click (PPC) online advertising. In this type of advertising, the owners of websites that post the ads are paid based on how many site visitors click on the ads. Fraud occurs when a person, automated script, computer program or an auto clicker imitates a legitimate user of a web browser, clicking on such an ad without having an actual interest in the target of the ad's link in order to increase revenue. Click fraud is the subject of some controversy and increasing litigation due to the advertising networks being a key beneficiary of the fraud.
In databases an index is a data structure, part of the database, used by a database system to efficiently navigate access to user data. Index data are system data distinct from user data, and consist primarily of pointers. Changes in a database, may require indexes to be updated to maintain accurate user data accesses. Index locking is a technique used to maintain index integrity. A portion of an index is locked during a database transaction when this portion is being accessed by the transaction as a result of attempt to access related user data. Additionally, special database system transactions may be invoked to maintain and modify an index, as part of a system's self-maintenance activities. When a portion of an index is locked by a transaction, other transactions may be blocked from accessing this index portion. Index Locking Protocol guarantees that phantom read phenomenon won't occur. Index locking protocol states:
A nested transaction is a database transaction that is started by an instruction within the scope of an already started transaction.
For transaction processing in computing, the X/Open XA standard is a specification released in 1991 by X/Open for distributed transaction processing (DTP).
In computer science and engineering, transactional memory attempts to simplify concurrent programming by allowing a group of load and store instructions to execute in an atomic way. It is a concurrency control mechanism analogous to database transactions for controlling access to shared memory in concurrent computing. Transactional memory systems provide high-level abstraction as an alternative to low-level thread synchronization. This abstraction allows for coordination between concurrent reads and writes of shared data in parallel systems.
Commitment ordering (CO) is a class of interoperable serializability techniques in concurrency control of databases, transaction processing, and related applications. It allows optimistic (non-blocking) implementations. With the proliferation of multi-core processors, CO has also been increasingly utilized in concurrent programming, transactional memory, and software transactional memory (STM) to achieve serializability optimistically. CO is also the name of the resulting transaction schedule (history) property, defined in 1988 with the name dynamic atomicity. In a CO compliant schedule, the chronological order of commitment events of transactions is compatible with the precedence order of the respective transactions. CO is a broad special case of conflict serializability and effective means to achieve global serializability across any collection of database systems that possibly use different concurrency control mechanisms.
M. Dale Skeen is an American computer scientist. He specializes in designing and implementing large-scale computing systems, distributed computing and database management systems.
Mostafa Abdel-Hamid el-Abbadi was a prominent Egyptian historian, public intellectual and professor specialized in Greco-Roman studies. He died on 13 February 2017, at the age of 88, in Alexandria.
Amr El Abbadi is a Distinguished Professor of Computer Science at the University of California, Santa Barbara. He obtained B.Eng. and Ph.D. degrees from Alexandria and Cornell universities, respectively. He is an editor of the VLDB Journal and IEEE Transactions on Computers. He was named Fellow of the Institute of Electrical and Electronics Engineers (IEEE) in 2014 for contributions to the design of fault-tolerant large-scale data management systems.
Gustavo Alonso is a Spanish/Swiss researcher in the areas of Computer Science and Electrical Engineering. He is a full professor at the Department of Computer Science and associated with the Department of Information Technology and Electrical Engineering of ETH Zürich. He is the head of the Institute of Computing Platforms, an ACM Fellow, and IEEE Fellow, winner of the Lifetime Achievements Award of EuroSys, and distinguished alumnus of the Department of Computer Science of UC Santa Barbara.
Database scalability is the ability of a database to handle changing demands by adding/removing resources. Databases use a host of techniques to cope.
Examples of coherency protocols for cache memory are listed here. For simplicity, all "miss" Read and Write status transactions which obviously come from state "I", in the diagrams are not shown. They are shown directly on the new state. Many of the following protocols have only historical value. At the moment the main protocols used are the R-MESI type / MESIF protocols and the HRT-ST-MESI or a subset or an extension of these.
References
- D. Agrawal, A. El Abbadi, A. E. Lang: The Performance of Protocols Based on Locks with Ordered Sharing, IEEE Transactions on Knowledge and Data Engineering, Volume 6, Issue 5, October 1994, pp. 805–818, ISSN 1041-4347
- Mahmoud, H. A., Arora, V., Nawab, F., Agrawal, D., & El Abbadi, A. (2014). Maat: Effective and scalable coordination of distributed transactions in the cloud. Proceedings of the VLDB Endowment, 7(5), 329-340.
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