Post by account_disabled on Oct 22, 2023 6:18:20 GMT
Concurrency control involves the synchronization of concurrent access to a distributed database to maintain the integrity of the database. If the result of the concurrent execution of a set of transactions on the database is equivalent to some kind of serial (one after another) execution of the same set of transactions, it can be said that the concurrently executed transactions maintain the consistency of the distributed database. This is called the serializability condition. From the perspective of ACID characteristics, the concurrency control algorithm maintains the consistency and isolation of transactions.
Concurrency control of distributed transactions requires a distributed synchronization algorithm that must ensure that concurrent transactions are not only serializable at each site where they execute, but also globally. This means that they must be executed in the same order at each site.
Distributed concurrency Mobile Number List algorithm can be divided into two categories: pessimistic algorithm and optimistic algorithm. The former synchronizes the execution of user requests before the transaction starts, and the latter executes the request and then performs verification checks to ensure execution. Transaction consistency will not be compromised. database. Two basic primitives that can be used with both methods are locking, which is based on mutual exclusion of access to data items (similar to semaphores in operating systems), and timestamping, where transactions are executed in some order. There are many variations of these schemes, as well as hybrid algorithms that attempt to combine the two basic mechanisms. Lock-based algorithms can lead to distributed deadlocks, requiring protocols to handle them (see Distributed Deadlock Detection).
Distributed Reliability Protocol Distributed database systems may be more reliable because there are multiple copies of each system component, which eliminates single points of failure, and data can be replicated to ensure access is provided in the event of a system failure. Distributed reliability protocols maintain atomicity and durability properties by: (a) ensuring that all operations of transactions executed at different sites complete successfully (called commits) or that none of them complete successfully (called aborts), and (b) ) ensures that modifications made to the database by committed transactions do not fail. (see Commit Protocol), while the second requires the recovery protocol. The most common atomic commit protocol is two-phase commit (2PC), in which transactions are committed in two steps: all sites that have executed the transaction are first polled to ensure that they are ready to commit, and then they are instructed to actually commit the transaction (see Two-Phase Commit ). The result is a uniform commitment (or abort) at every site where a transaction is executed. Recovery protocols are the opposite of atomic commitment protocols. They ensure that the system can be restored to a consistent state after a failure.
Concurrency control of distributed transactions requires a distributed synchronization algorithm that must ensure that concurrent transactions are not only serializable at each site where they execute, but also globally. This means that they must be executed in the same order at each site.
Distributed concurrency Mobile Number List algorithm can be divided into two categories: pessimistic algorithm and optimistic algorithm. The former synchronizes the execution of user requests before the transaction starts, and the latter executes the request and then performs verification checks to ensure execution. Transaction consistency will not be compromised. database. Two basic primitives that can be used with both methods are locking, which is based on mutual exclusion of access to data items (similar to semaphores in operating systems), and timestamping, where transactions are executed in some order. There are many variations of these schemes, as well as hybrid algorithms that attempt to combine the two basic mechanisms. Lock-based algorithms can lead to distributed deadlocks, requiring protocols to handle them (see Distributed Deadlock Detection).
Distributed Reliability Protocol Distributed database systems may be more reliable because there are multiple copies of each system component, which eliminates single points of failure, and data can be replicated to ensure access is provided in the event of a system failure. Distributed reliability protocols maintain atomicity and durability properties by: (a) ensuring that all operations of transactions executed at different sites complete successfully (called commits) or that none of them complete successfully (called aborts), and (b) ) ensures that modifications made to the database by committed transactions do not fail. (see Commit Protocol), while the second requires the recovery protocol. The most common atomic commit protocol is two-phase commit (2PC), in which transactions are committed in two steps: all sites that have executed the transaction are first polled to ensure that they are ready to commit, and then they are instructed to actually commit the transaction (see Two-Phase Commit ). The result is a uniform commitment (or abort) at every site where a transaction is executed. Recovery protocols are the opposite of atomic commitment protocols. They ensure that the system can be restored to a consistent state after a failure.