Key takeaways
- Lamport and vector clocks, election, mutual exclusion and 2PC appear in almost every paper.
- Draw timeline diagrams for clock and election questions; they earn marks quickly.
- Each section has exam tips and formula boxes, and the last page lists the most asked practice questions.
- These are original Uncodemy revision notes, not official university notes; check your own syllabus.
About these Distributed Systems handwritten notes
This page offers Uncodemy's Distributed Systems notes as a free handwritten-style PDF. Distributed Systems studies many independent computers that work together and appear to users as one system. The notes are written in short points with neat tables, labelled diagrams, boxed formulas and exam tips, so you can revise a full unit in one sitting instead of reading a long textbook chapter.
Please note: these are original Uncodemy revision notes. They follow the common syllabus that most Indian universities share for this subject, but they are not official university notes. Check your own university syllabus and add anything it lists that is missing here.
What's inside the Distributed Systems notes
The PDF is arranged in 8 sections plus a final page of most asked practice questions. The sections follow the usual unit order of a Distributed Systems syllabus, so you can map them to your own units quickly. Here is what each section covers.
Introduction
Definition, goals, types of transparency such as access, location and replication, and the main challenges.
System models and architecture
Client-server and peer-to-peer architectures, interaction models and failure models.
Communication
RPC with stubs and call semantics, RMI and message passing.
Time and clock synchronisation
Cristian's and Berkeley algorithms for physical clocks, and Lamport and vector clocks for logical time.
Mutual exclusion and election
Centralised, token ring and Ricart-Agrawala mutual exclusion, and the Bully and Ring election algorithms.
Consistency and replication
Why replicas are used, consistency models from strict to eventual, the CAP theorem and quorum-based replication.
Fault tolerance and agreement
Failure handling, the two-phase commit protocol and its blocking problem, three-phase commit and consensus.
Distributed file systems and shared memory
The design of systems such as NFS and HDFS, and distributed shared memory.
Most asked questions (practice)
Ten exam-style questions, from transparency to HDFS and NFS architecture.
How to use handwritten notes to revise Distributed Systems
Distributed Systems is mostly algorithms explained with diagrams, so revise each algorithm in the notes as a picture first and text second.
- Assign Lamport and vector timestamps to events on a three-process timeline.
- Trace the Bully algorithm when the coordinator fails, showing every message.
- Compare mutual exclusion algorithms in a table by messages per entry and failure handling.
- Draw the two-phase commit message flow and mark where the coordinator failure blocks it.
A simple three-pass method works well with handwritten notes. In the first pass, read one section and underline only what you do not already know. In the second pass, close the notes and write the definitions, diagrams and steps for that section on a blank sheet, then compare and correct in a different colour. In the third pass, a day or two later, answer two or three exam-style Distributed Systems questions in timed conditions using only memory. Add your own examples and doubts in the margins so the PDF becomes your personal revision copy.
Formulas, diagrams and definitions to memorise
- Lamport clock rules: increment before each event, and on receive set the clock to max(local, received) + 1.
- Vector clock rules and how to compare two vectors to decide causality or concurrency.
- Cristian's algorithm estimate: server time + round trip time / 2.
- CAP theorem: during a network partition a system must choose consistency or availability.
- The two-phase commit message flow: prepare, vote, then commit or abort.
Common mistakes that cost marks
- Concluding that one event happened before another just because its Lamport timestamp is smaller.
- Mixing up the Bully algorithm (highest ID wins by challenging higher IDs) with the Ring algorithm.
- Describing CAP as choosing two of three at all times; the trade-off matters during a partition.
- Leaving out the blocking problem when explaining two-phase commit.
Exam focus: Distributed Systems topics that carry the most marks
These Distributed Systems topics carry the most marks in most university papers.
- Goals and transparency types.
- RPC and its call semantics.
- Clock synchronisation, Lamport clocks and vector clocks.
- Mutual exclusion, election algorithms, CAP theorem and two-phase commit.
Typical long questions
- Define distributed systems and explain the types of transparency.
- Explain RPC with a diagram and its call semantics.
- Explain Cristian's and Berkeley clock synchronisation.
- Explain Lamport clocks and vector clocks with examples.
- Explain the Bully and Ring election algorithms.
- Explain the CAP theorem and consistency models.
- Explain the two-phase commit protocol and its problem.
Marks per question change between universities and years, so confirm the pattern on a recent official paper. In long answers, start with a definition, add a labelled diagram or table, explain the steps and finish with an example or comparison. Underline the key term in each answer and leave a line between steps, because examiners mark faster when the structure is easy to see.
A 7-day revision plan for Distributed Systems
- Day 1: Introduction, System models and architecture.
- Day 2: Communication, Time and clock synchronisation.
- Day 3: Mutual exclusion and election, Consistency and replication.
- Day 4: Fault tolerance and agreement.
- Day 5: Distributed file systems and shared memory.
- Day 6: redo the traces: Lamport and vector timestamps, one Bully election, one Ricart-Agrawala request and the 2PC flow.
- Day 7: answer the most asked practice questions at the end of the notes from memory, then solve one official previous year paper in three hours and mark the units that cost you time.
Keep a single sheet of formulas, definitions and diagrams from the notes for the last hour before the exam, and do not start new topics on the final day.
Who these notes are for
- B.Tech CSE and IT students preparing for the semester Distributed Systems or Distributed Computing exam.
- MCA and M.Tech students with a distributed systems paper.
- Students moving into cloud, DevOps or backend work who want the theory behind replicated systems.
- Freshers preparing for system design rounds who need clear basics on consistency and fault tolerance.
The notes are a revision aid, not a first textbook. If a Distributed Systems topic is new to you, learn it from your prescribed book or class lectures first, then come back to the notes to compress and revise it. For practice, pair them with the Cloud Computing Important Questions PDF page and your university's official previous year papers. If your syllabus has a topic that is not covered here, you can ask for it through the handwritten notes request page linked below.
Download Distributed Systems Handwritten Notes PDF
Distributed Systems Handwritten Notes PDF (Free)
The PDF carries the same content as this page in a clean, print-ready layout, so you can read it offline and keep it for revision.
7 pages · 260 KB · PDF · Updated 5 Nov 2026