Gateforum Test Series: Databases - Transactions

Question

Which of the following is false?

a)All the schedules which are allowed under basic time stamp ordering protocols are also allowed under Thomas write rule.

b)Schedules which are allowed under Thomas write rule are also allowed under multi-version timestamp ordering protocol.

c)All the schedules which are not allowed Thomas write rule are also not allowed in a multi-version timestamp ordering protocol.

d)None.

Answer 1

The hierarchy is like this :

$I$ is $false,$ Some allowed under basic timestamp are not allowed under thomas write rule

$II$ is $false,$ Some allowed under thomas write rule are not allowed under multiversion timestamp ordering protocol

$III$ is $false,$ Some not allowed under thomas are allowed under multiversion

Comments

can you please mention the source from where you have referred the pic?

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actually i created this on my own. I remember this from a solution of a question from testbook test, basic timestamp and thomas write relation can be easily seen, I don't know about multi-version, though I am sure testbook would not be wrong in this solution. If I find a source i will post it here.

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https://gateoverflow.in/217350/understanding-multiversion-timestamp-ordering-protocol 

i have referred the above link in which it is mentioned that multiversion timestamp ordering is superset of thomas write rule. So according to this the option B is true and option C is false and from this link and korth https://www.geeksforgeeks.org/dbms-concurrency-control-protocol-thomas-write-rule/  they have mentioned that all the possible scheules under basic timestamp are also allowed in thomas write rule. So option A is true.