11introductiontotransactionprocessing2

School: University of Wollongong - Course: CSCI 235 - Subject: Accounting

CSCI235 Database Systems Introduction to Transaction Processing (2) Dr Janusz R. Getta School of Computing and Information Technology - University of Wollongong Introduction to Transaction Processing (2)file:///Users/jrg/235-2020-AUTUMN/LECTURES/WEEK05/11introductiontotransproc2/11introductiont... 715/4/20, 10:31 pm

Introduction to Transaction Processing Outline Correctness Conﬂict serializability versus view serializability Order preserving conﬂict serializability Recoverable executions Cascadeless executions Strict executions TOP Created by Janusz R. Getta,CSCI235 Database Systems,Autumn 20202/27 Introduction to Transaction Processing (2)file:///Users/jrg/235-2020-AUTUMN/LECTURES/WEEK05/11introductiontotransproc2/11introductiont... 715/4/20, 10:31 pm

Correctness What makes concurrent execution of database transaction incorrect ? How do we define a correct concurrent execution of database transactions ? Concurrent execution of database transactions is view serializable if there exists a possible serial execution of the same set of transactions such that in both executions each transaction reads the same values and the final states of the database are the same A concurrent execution of database transactions is correct when it is view serializable TOP Created by Janusz R. Getta,CSCI235 Database Systems,Autumn 20203/27 Introduction to Transaction Processing (2)file:///Users/jrg/235-2020-AUTUMN/LECTURES/WEEK05/11introductiontotransproc2/11introductiont... 715/4/20, 10:31 pm

Correctness A sample view serializable execution of database transactions The execution of database transactions above is view serializable because there exists a serial execution of the same transactions such that in both executions the transactions read the same values and the final states of the database are the same (see next slide)