Answer: Coordinator Site / Originating Site
Answer: High availability and reliability
Answer: Process of defining and maintaining global and local user views of distributed data
Answer: Communication cost, CPU cost, I/O cost, data location, response time
Answer: Lock-based, Timestamp-based, Optimistic protocol
Answer: Multiple processors share a common memory and disk
Answer: To maintain availability and synchronization of data
Answer: Two Phase Commit (2PC)
Answer: Dividing database into smaller fragments distributed across sites
Answer: Atomicity, Consistency, Isolation, Durability (ACID)
Answer: Shared Memory, Shared Disk, Shared Nothing
Answer: Managing distributed objects and providing transparent access
Concurrency control ensures multiple transactions execute simultaneously without inconsistency. Lock-Based Protocol: transactions lock data before access (Shared/Exclusive locks). Example: T1 locks A, updates, unlocks; T2 waits. Prevents lost updates but may cause deadlock.
Location Transparency: user unaware of physical location. Replication Transparency: multiple copies appear as one. Fragmentation Transparency: user sees complete relation despite fragmentation.
Database supporting wireless access, replication, synchronization. Applications: banking, healthcare, e-commerce. Advantages: anywhere access; disadvantages: security concerns.
Advantages: high availability, faster access, fault tolerance. Disadvantages: storage overhead, sync complexity. Auxiliary Program: coordinates replicas, monitors updates, maintains consistency.
MDBS (Multi-Database System): integrates autonomous databases. Architecture: Users → Global Schema → MDBMS → Local Databases. Advantages: autonomy, scalability; disadvantage: integration complexity.
Flat Transaction: single atomic unit (BEGIN → COMMIT/ABORT). Nested Transaction: parent with child sub-transactions, supports parallelism. Distributed Transaction: runs across multiple sites (e.g., bank transfer). Chained Transaction: sequence of independent commits. Workflow Transaction: business-process oriented. Advantages: reliability, parallelism.
Ensures all sites either commit or abort → atomicity in distributed transactions. Needed for consistency, failure handling, recovery. Example: bank transfer (debit success, credit failure) would cause inconsistency without protocol. Protocols: Two-Phase Commit (2PC), Three-Phase Commit (3PC).
Shared Memory: multiple CPUs share memory/disk → fast but limited scalability. Shared Disk: each CPU private memory, shared disk → high availability, disk contention. Shared Nothing: each node has CPU+memory+disk → highly scalable, complex communication.
| Architecture | Scalability | Fault Tolerance |
|---|---|---|
| Shared Memory | Low | Medium |
| Shared Disk | Medium | High |
| Shared Nothing | High | Very High |
Coordinator: START → Send PREPARE → Receive VOTES → COMMIT/ABORT → Send decision. Participant: Receive PREPARE → Vote YES/NO → Wait → COMMIT/ABORT.
Phases: Voting Phase (Coordinator sends PREPARE, participants vote) and Decision Phase (Coordinator sends COMMIT/ABORT). Ensures atomic distributed commit.
Components: Global Schema, Local Schema, MDBMS. Architecture: Users → MDBMS → Local Databases. Advantages: data sharing, autonomy, scalability. Disadvantages: integration complexity, query optimization overhead.
Database accessible via mobile devices with wireless access, replication, synchronization. Features: portability, intermittent connectivity, data caching. Applications: GPS, banking, navigation, e-commerce.
Methods: Locking (2PL), Timestamp-based (older transaction priority), Optimistic validation, Distributed 2PL. Benefits: isolation, consistency, deadlock handling.
✔ Complete coverage of MAKAUT Distributed Systems (PEC-IT601B) – Groups A, B, and C.
✔ Includes transaction models, concurrency control, 2PC, parallel architectures, transparency, replication, mobile databases, multidatabase architecture, and concurrency algorithms.
✔ Answers structured for 1, 5, and 15-mark questions with definitions, tables, diagrams, and exam-style presentation.