Design a fragmentation strategy to ensure that London projects are only in London and New York projects are only in New York.
You have a global relation Employee (EmpID, Name, Dept, Salary, Location) . You need to fragment this based on the query: "Find employees working in New York or London." Solution Approach:
: Draw a timeline. For T/O, always compare the transaction’s timestamp with the Read-TS and Write-TS of the data item. For 2PL, check lock compatibility matrices and ensure no lock release before the end of the transaction.
Reliability protocols ensure that an atomic transaction executes completely across all participating nodes or fails cleanly everywhere. Two-Phase Commit (2PC) Execution Step-by-Step Design a fragmentation strategy to ensure that London
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by M. Tamer Özsu and Patrick Valduriez (3rd and 4th editions) are primarily restricted to instructors. However, students can access several high-quality alternative resources for practice. University of Waterloo 1. Official Companion Sites (Instructor Restricted)
The highest level of transparency. The user operates on a single global relation without knowing if or how the data is split into fragments. For T/O, always compare the transaction’s timestamp with
: Always check quorum sizes against available nodes in the partition. The intersection property (R+W > N) guarantees consistency only in a non-partitioned system. During partitions, you must choose between availability and consistency (CAP theorem).
You will draw state-transition diagrams to visualize the "prepare" and "commit" phases. Tips for Acing Your Distributed Database Exams
: If T2 tried to Write(X) before T1’s Read(X), and T2 > T1, T/O would reject it, aborting T2. Common Exercise Scenario:
Is there a way to do this with fewer bytes?
The Coordinator writes a [prepare, T] record to its log and sends a message to all participants.
A banking application allows users to query account balances globally. A query is written as SELECT balance FROM accounts WHERE location = 'New York' AND id = 101 . However, if the data moves to a server in London, the query must be rewritten to target a different table name ( accounts_uk ). What level of transparency is missing? Solution & Analytical Framework
Dividing a relation into subsets of attributes (columns). Solutions focus on grouping attributes frequently accessed together, often using an Attribute Affinity Matrix . Common Exercise Scenario: