Principles Of Distributed Database Systems Exercise Solutions //free\\ File

Consider a global relation EMP(ENO, ENAME, TITLE) and PROJ(PNO, PNAME, BUDGET) . There is a relationship relation ASG(ENO, PNO, RESPONSIBILITY, DUR) .

Upon restart, coordinator sends COMMIT to P3 (if decision logged). If no decision logged and some participant already committed (via unilateral decision), P3 must commit → but this violates 2PC’s blocking property? Actually, 2PC can block if coordinator crashes without decision. That’s why 3PC is non-blocking. Consider a global relation EMP(ENO, ENAME, TITLE) and

These are common algorithmic solutions for deadlock prevention. If no decision logged and some participant already

What happens if the coordinator fails after the voting phase? Solution: This is the "blocking problem" of 2PC. Participants may be left in an uncertain state, holding locks indefinitely until the coordinator recovers. This is why modern systems often look toward Three-Phase Commit (3PC) or Paxos/Raft consensus algorithms. 5. Parallelism and Data Replication Consider a global relation EMP(ENO

Transaction T updates items A (site1) and B (site2). Show the steps for atomic commitment using WAL and 2PC.

If a query only needs Name and Salary , you would use a PROJECT operation to split columns rather than rows.

F1 = σ_Dept=‘Sales’(EMPLOYEE) F2 = σ_Dept=‘Eng’(EMPLOYEE) F3 = σ_Dept≠‘Sales’ ∧ Dept≠‘Eng’(EMPLOYEE)