Principles Of Distributed Database Systems Exercise Solutions Jun 2026
Employee=EmployeeVF1⋈EmpIDEmployeeVF2Employee equals Employee sub cap V cap F 1 end-sub ⋈ sub EmpID end-sub Employee sub cap V cap F 2 end-sub Horizontal: If a tuple appears in fragment Ricap R sub i , it must not appear in any other fragment Rjcap R sub j ). Since the predicates are mutually exclusive ( ), the fragments are strictly disjoint:
Better is to perform parallel hash join: each site joins locally on its own bucket after exchanging only needed buckets (cost = same total data volume). So 60,000 is correct.
What is replication in a distributed database system? What is replication in a distributed database system
If an older transaction requests a resource held by a younger transaction, the older waits. If a younger transaction requests a resource held by an older one, the younger dies. T1cap T sub 1 (old) requests T2cap T sub 2 →right arrow T1cap T sub 1 Waits .2. T2cap T sub 2 (young) requests T1cap T sub 1 →right arrow T2cap T sub 2 Dies . T2cap T sub 2 aborts and releases , allowing T1cap T sub 1 to proceed. Wound-Wait (Preemptive)
Detecting deadlocks that involve resources across different nodes (e.g., Wait-For Graphs). T1cap T sub 1 (old) requests T2cap T
Cost=10,000×40 bytes=400,000 bytesCost equals 10 comma 000 cross 40 bytes equals 400 comma 000 bytes Strategy B: Semi-Join Program
). Minterm predicates are conjunctions (AND operations) of every primitive predicate or its negation. When solving distributed database system problems
When solving distributed database system problems, keep these fundamental principles in mind:
A distributed deadlock detector must abort one of the transactions (typically the youngest via the Wait-Die or Wound-Wait scheme) to break the cycle. 4. Distributed Reliability & Commit Protocols Two-Phase Commit (2PC) State Machine Analysis Coordinator Phase Cohort Phase 1. Sends PREPARE 1. Receives PREPARE 2. Collects Votes 2. Sends VOTE_COMMIT / VOTE_ABORT 3. Broadcasts COMMIT / ABORT 3. Executes command
