23. Two Phase Locking (2PL) | System Design

➡️ Notes: Shared in the Member Community Post (If you are Member of this channel, then pls check the Member community post, i have shared the Notes link there)

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Topics i have covered:

- Basic 2PL and its issues (Deadlock and Cascading Abort)
- Conservative 2PL
- Rigorous 2PL

Chapters:
00:00 - Introduction
00:41 - Basic 2PL
08:56 - Deadlock, 1st Issues with Basic 2PL
14:30 - Timeout, Deadlock Prevention Strategy
16:30 - WFG(Wait for Graph), Deadlock Prevention Strategy
21:42 - Conservative 2PL, Deadlock Prevention Strategy
24:52 - TimeStamp, Deadlock Prevention Strategy
29:14 - Cascading Abort, 2nd Issue with Basic 2PL
32:37 - Rigorous or (Strong Strict 2PL), Cascading Abort Prevention Strategy
34:45 - Example of Each

#concurrency #systemdesign #softwareengineer

[shamstabrez]

kya admi ho bhai u r covering all the important system design concepts keep going keep doing sch kind an amazing work we r here to support u

[saurabhtiwari]

Kl hi DBMS revise kra tha aaj aapka lecture deekha. Kasam se aatma tript ho gyi.🎉🎉🎉

Ek request or h sir. Agar aap small small practiceal demo ki video bhi provide krwa de toh mza aa jayegaa. 😊😊😊

[mayankkumarprajapati]

again, very good video, really liked the detailed explanation

[priyanshnamdeo]

In the 35:04 example ; since we are dealing with Basic 2PL ; txn 1 should acquire locks on both A and B during the growing phase, that way there shouldn't be an issue, Correct me if I am wrong ; the example that you have have cited for Basic 2PL seem to be violating the Basic 2PL principle .

[baburaomulaparthi]

explanation is very good bro, can you share programming examples.

[garimadhanania]

One question: The last example that you take at 35:00 for basic 2PL, did you come up with or if not, could you please share the source of it?
Its odd that you one would update A (commit) before crediting to B. I assumed that credit debit kind of transactions happen in an atomic manner. In basic 2PL the locks could be release before the commit, but when the commit happens both A and B's value would be changed. Thats how I imagine correct "atomic transaction" to be implemented

[anshulkatare]

If transactions can release a lock on a resouce as per their wish, then its not really a Repeatable Read isolation level or higher.
Which says a txn will keep shared lock or Exclusive lock till the end of txn. How does isolation level and unlock at will work together?

[akhilnama]

Hi really liked your content, it will be very helpful if you can please make notes available for other videos also. Thanks

[prateekkanujiya]

Hi Shreyansh, Could you please suggest how can we achieve 2PL using Java ?

[prashantkumar-hxdv]

Where is the link for getting the membership of "channel's members on level: Unlock LLD, HLD and JAVA (or any higher level)." Please tell. I have only limited access.

[AkashYadav-ijwe]

Good theory, it would be better if we could have also implemented each of them. Just a simple demo.

[ApoorvBansal-sd]

Hi sir, in case of Basic 2 Phase locking can we prevent deadlock at code level also by making request serializable and access of critical section by using semaphore and mutexes.

[saurabhmittal]

in the example shown at 30:40, I assume, we are using Repeatable read isolation level then how is txn1 is able to release the write lock in middle ? shouldn't it release at after commit ??

[srijandasbiswas]

Can you please make a video on jwt token, OAuth authentication . It will be extremely helpful

[dhanashripatkar]

Hi Shreyash, thanks for spreading this knowledge in a simple and easier way. One request for you, can you please create a video on Docker. Many times conceptual questions based on Docker were asked me in an interview. Also, in one system design interview, I was asked to design an "Online Code compiler System which supports many programming languages". How to do this with docker implementation?

[SaiPhaniRam]

Timestamp 27:56

If TXN 1 has Higher Priority compared to TXN 2, then how come TXN 2 Exclusively locks the record A earlier ?
The very point of precedence is not served right?

[anantsingh]

Hi shrayansh, bhai your 2 videos are unavailable in this playlist ex - hld of url shortening service, where/how can I watch it ?

[zainulabidin]

Hi Shrayansh,

Cascading abort as per my understanding is the dirty read problem, in your previous video you told that pessimistic locking is done for isolation levels "Repeatable Read" and "Serialization" in which dirty read can not be done. Can you kindly clear this please?

[anadilfaridy]

I see only 2 deadlock prevention strategy timeout and graph but in video you said you explained all 4, am i missing something?

[ShashikantPawar-gu]

Can you please complete this series as per roadmap in first video