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The introduction of granular (subset) locks creates the possibility for a situation called deadlock. Deadlock is possible when incremental locking (locking one entity, then locking one or more additional entities) is used. To illustrate, if two bank customers asked two clerks to obtain their account information so they could transfer some money ...
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.
The term "deadlock avoidance" appears to be very close to "deadlock prevention" in a linguistic context, but they are very much different in the context of deadlock handling. Deadlock avoidance does not impose any conditions as seen in prevention but, here each resource request is carefully analyzed to see whether it could be safely fulfilled ...
This subtlety can increase the chance that a programmer will unknowingly introduce a deadlock. [citation needed] In a database management system, for example, a lock could protect, in order of decreasing granularity, part of a field, a field, a record, a data page, or an entire table. Coarse granularity, such as using table locks, tends to give ...
Mimer SQL is a DBMS that only implements optimistic concurrency control. [10] Google App Engine data store uses OCC. [11] The Apache Solr search engine supports OCC via the _version_ field. [12] The Elasticsearch search engine updates its documents via OCC. Each version of a document is assigned a sequence number, and newer versions receive ...
Deadlock freedom can be expanded to implement one or both of these properties: Lockout-freedom guarantees that any process wishing to enter the critical section will be able to do so eventually. This is distinct from deadlock avoidance , which requires that some waiting process be able to get access to the critical section, but does not require ...
The forced wait policy may involve waiting for higher priority transactions to process in order to prevent deadlock. Another example of when data can be delayed is when a block of data is about to expire. The forced wait policy delays processing until the data is updated using new input data.
Race condition in a logic circuit. Here, ∆t 1 and ∆t 2 represent the propagation delays of the logic elements. When the input value A changes from low to high, the circuit outputs a short spike of duration (∆t 1 + ∆t 2) − ∆t 2 = ∆t 1.