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Lease (computer Science)
In computer science, a Lease is a contract that gives its holder specified rights to some resource for a limited period. Because it is time-limited, a lease is an alternative to a lock for resource serialization. Motivation A traditional resource lock is granted until it is explicitly released by the locking client process. Reasons why a lock might not be released include: * The client failed before releasing the resources * The client deadlocked while attempting to allocate another resource * The client was blocked or delayed for an unreasonable period * The client neglected to free the resource, perhaps due to a bug * The request to free the resource was lost * The resource manager failed or lost track of the resource stated Any of these could end the availability of an important reusable resource until the system is reset. By contract, a lease is valid for a limited period, after which it automatically expires, making the resource available for reallocation by a new client ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical disciplines (including the design and implementation of Computer architecture, hardware and Computer programming, software). Computer science is generally considered an area of research, academic research and distinct from computer programming. Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and for preventing Vulnerability (computing), security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Progr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lock (computer Science)
In computer science, a lock or mutex (from mutual exclusion) is a synchronization primitive: a mechanism that enforces limits on access to a resource when there are many threads of execution. A lock is designed to enforce a mutual exclusion concurrency control policy, and with a variety of possible methods there exists multiple unique implementations for different applications. Types Generally, locks are ''advisory locks'', where each thread cooperates by acquiring the lock before accessing the corresponding data. Some systems also implement ''mandatory locks'', where attempting unauthorized access to a locked resource will force an exception in the entity attempting to make the access. The simplest type of lock is a binary semaphore. It provides exclusive access to the locked data. Other schemes also provide shared access for reading data. Other widely implemented access modes are exclusive, intend-to-exclude and intend-to-upgrade. Another way to classify locks is by what hap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serialization
In computing, serialization (or serialisation) is the process of translating a data structure or object state into a format that can be stored (e.g. files in secondary storage devices, data buffers in primary storage devices) or transmitted (e.g. data streams over computer networks) and reconstructed later (possibly in a different computer environment). When the resulting series of bits is reread according to the serialization format, it can be used to create a semantically identical clone of the original object. For many complex objects, such as those that make extensive use of references, this process is not straightforward. Serialization of object-oriented objects does not include any of their associated methods with which they were previously linked. This process of serializing an object is also called marshalling an object in some situations. The opposite operation, extracting a data structure from a series of bytes, is deserialization, (also called unserialization or un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Bug
A software bug is an error, flaw or fault in the design, development, or operation of computer software that causes it to produce an incorrect or unexpected result, or to behave in unintended ways. The process of finding and correcting bugs is termed " debugging" and often uses formal techniques or tools to pinpoint bugs. Since the 1950s, some computer systems have been designed to deter, detect or auto-correct various computer bugs during operations. Bugs in software can arise from mistakes and errors made in interpreting and extracting users' requirements, planning a program's design, writing its source code, and from interaction with humans, hardware and programs, such as operating systems or libraries. A program with many, or serious, bugs is often described as ''buggy''. Bugs can trigger errors that may have ripple effects. The effects of bugs may be subtle, such as unintended text formatting, through to more obvious effects such as causing a program to crash, freezing th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cary G
Cary may refer to: Places ;United States * Cary, Illinois, part of the Chicago metropolitan area * Cary, Indiana, part of the Indianapolis metropolitan area * Cary, Miami County, Indiana * Cary, Maine * Cary, Mississippi * Cary, North Carolina, part of the Research Triangle * Cary, Wisconsin ;United Kingdom * Cary (barony), County Antrim, Northern Ireland * Castle Cary, Somerset, England Other uses * Cary (given name) * Cary (surname) * Cary Academy * Cary Audio Design, manufacturer of vacuum tube and solid state audio components * Cary Instruments, the optical instrumentation division of Varian Instruments * River Cary * Typhoon Cary, the name of three tropical cyclones in the western north Pacific Ocean See also * Carey (other) * Caries, a progressive destruction of any kind of bone structure * Carrie (other) * Carry (other) * Kary (other) Kary may refer to: * Kary (name), is both a surname and a given name * Kary, South Dakota, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
David R
David (; , "beloved one") (traditional spelling), , ''Dāwūd''; grc-koi, Δαυΐδ, Dauíd; la, Davidus, David; gez , ዳዊት, ''Dawit''; xcl, Դաւիթ, ''Dawitʿ''; cu, Давíдъ, ''Davidŭ''; possibly meaning "beloved one". was, according to the Hebrew Bible, the third king of the United Kingdom of Israel. In the Books of Samuel, he is described as a young shepherd and harpist who gains fame by slaying Goliath, a champion of the Philistines, in southern Canaan. David becomes a favourite of Saul, the first king of Israel; he also forges a notably close friendship with Jonathan, a son of Saul. However, under the paranoia that David is seeking to usurp the throne, Saul attempts to kill David, forcing the latter to go into hiding and effectively operate as a fugitive for several years. After Saul and Jonathan are both killed in battle against the Philistines, a 30-year-old David is anointed king over all of Israel and Judah. Following his rise to power, David ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DHCP
The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a client–server architecture. The technology eliminates the need for individually configuring network devices manually, and consists of two network components, a centrally installed network DHCP server and client instances of the protocol stack on each computer or device. When connected to the network, and periodically thereafter, a client requests a set of parameters from the server using DHCP. DHCP can be implemented on networks ranging in size from residential networks to large campus networks and regional ISP networks. Many routers and residential gateways have DHCP server capability. Most residential network routers receive a unique IP address within the ISP network. Within a local network, a DHCP server assigns a local IP address to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File Locking
File locking is a mechanism that restricts access to a computer file, or to a region of a file, by allowing only one user or process to modify or delete it at a specific time and to prevent reading of the file while it's being modified or deleted. Systems implement locking to prevent the classic ''interceding update'' scenario, which is a typical example of a race condition, by enforcing the serialization of update processes to any given file. The following example illustrates the interceding update problem: # Process A reads a customer record from a file containing account information, including the customer's account balance and phone number. # Process B now reads the same record from the same file, so it has its own copy. # Process A changes the account balance in its copy of the customer record and writes the record back to the file. # Process B, which still has the original ''stale'' value for the account balance in its copy of the customer record, updates the account balan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Access Token
In computer systems, an access token contains the security credentials for a login session and identifies the user, the user's groups, the user's privileges, and, in some cases, a particular application. In some instances, one may be asked to enter an access token (e.g. 40 random characters) rather than the usual password (it therefore should be kept secret just like a password). Overview An ''access token'' is an object encapsulating the security identity of a process or thread. A token is used to make security decisions and to store tamper-proof information about some system entity. While a token is generally used to represent only security information, it is capable of holding additional free-form data that can be attached while the token is being created. Tokens can be duplicated without special privilege, for example to create a new token with lower levels of access rights to restrict the access of a launched application. An access token is used by Windows when a process or t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Transaction
In database systems, atomicity (; from grc, ἄτομος, átomos, undividable) is one of the ACID (''Atomicity, Consistency, Isolation, Durability'') transaction properties. An atomic transaction is an ''indivisible'' and ''irreducible'' series of database operations such that either ''all'' occurs, or ''nothing'' occurs. A guarantee of atomicity prevents updates to the database occurring only partially, which can cause greater problems than rejecting the whole series outright. As a consequence, the transaction cannot be observed to be in progress by another database client. At one moment in time, it has not yet happened, and at the next it has already occurred in whole (or nothing happened if the transaction was cancelled in progress). An example of an atomic transaction is a monetary transfer from bank account A to account B. It consists of two operations, withdrawing the money from account A and saving it to account B. Performing these operations in an atomic transaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
