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A wait-for graph in computer science is a directed graph used for deadlock detection in operating systems and relational database systems.. In computer science, a system that allows concurrent operation of multiple processes and locking of resources and which does not provide mechanisms to avoid or prevent deadlock must support a mechanism to detect deadlocks and an algorithm for recovering ...
To accommodate recovery from failure (automatic in most cases) the protocol's participants use logging of the protocol's states. Log records, which are typically slow to generate but survive failures, are used by the protocol's recovery procedures. Many protocol variants exist that primarily differ in logging strategies and recovery mechanisms.
In computer science, deadlock prevention algorithms are used in concurrent programming when multiple processes must acquire more than one shared resource.If two or more concurrent processes obtain multiple resources indiscriminately, a situation can occur where each process has a resource needed by another process.
In addition, in distributed databases, even the protocols for logging and recovery shall address the issues of distributed environments, such as deadlocks, that could prevent the resilience and recoverability of transactions and, thus, durability. [13]
Phantom deadlocks are deadlocks that are falsely detected in a distributed system due to system internal delays but do not actually exist. For example, if a process releases a resource R1 and issues a request for R2 , and the first message is lost or delayed, a coordinator (detector of deadlocks) could falsely conclude a deadlock (if the ...
In computer science, Algorithms for Recovery and Isolation Exploiting Semantics, or ARIES, is a recovery algorithm designed to work with a no-force, steal database approach; it is used by IBM Db2, Microsoft SQL Server and many other database systems. [1] IBM Fellow Chandrasekaran Mohan is the primary inventor of the ARIES family of algorithms. [2]
When the recovery coordinator takes over after the coordinator failed during a commit phase of two-phase commit, the new pre-commit comes handy as follows: On querying participants, if it learns that some nodes are in commit phase then it assumes that the previous coordinator before crashing has made the decision to commit. Hence it can ...
Furthermore, in such environment data-access-locking related global deadlocks are resolved automatically (each such deadlock is generated by a global cycle in the augmented conflict graph (i.e., a voting deadlock; see above), involving at least one data-access lock (non-materialized conflict) and two database systems; thus, not a cycle in the ...