Database transaction schedule: Difference between revisions

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====Cascadeless====

'''Cascadeless schedules''' (a.k.a,. "Avoiding Cascading Aborts (ACA) schedules") are schedules which avoid cascading aborts by disallowing [[Write–read conflict|dirty reads]]. '''Cascading aborts''' occur when one transaction's abort causes another transaction to abort because it read and relied on the first transaction's changes to an object. A '''dirty read''' occurs when a transaction reads data from uncommitted write in another transaction.<ref>{{Cite web |date=2019-08-06 |title=Cascadeless in DBMS |url=https://www.geeksforgeeks.org/cascadeless-in-dbms/ |access-date=2023-11-29 |website=GeeksforGeeks |language=en-US}}</ref>

The following examples are the same as the ones in the discussion on recoverable:

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Any strict schedule is cascade-less, but not the converse. Strictness allows efficient recovery of databases from failure.

== Serializability Classclass Relationshipsrelationships ==

The following expressions illustrate the hierarchical (containment) relationships between [[serializability]] and [[Serializability#Correctness - recoverability|recoverability]] classes: