banco de dados - Stack Overflow em Português Com o MVCC se obtém o isolamento e facilita a consistência e atomicidade do ACID e em alguns casos pode facilitar a durabilidade É um mecanismo simples e eficiente se bem implementado Cada transação é totalmente independente e livre de efeitos colaterais
Optimistic vs Multi Version Concurrency Control - Differences? To directly reply to the question, multi version concurrency control (MVCC) is a concurrency control method, (typically) belonging in the category of optimistic concurrency control (OCC)
How MVCC works with Lock in MySql? - Stack Overflow Do you want to express that MVCC implementation of MYSQL would not block the select (for update) in RR? In fact, what I want to ask is how to use MVCC and locks to solve phantom-reading, due to general definition of MVCC, it can achieve RR by inserting the undo-logs However, it seems that MVCC (lock-free) cannot avoid phantom reading without lock
Why xmin and xmax values are same in PostgreSQL? I've been learning MVCC in PostgreSQL As I understood, when the row is updated, a new row will be added and the xmax value in old row will have the value of the xmin of the newly added row When I checked it in the table I have in my Postgres DB, the xmin and xmax values are the same What does it mean?
Better concurrency in Oracle than SQL Server? - Stack Overflow 9 Out of the box, Oracle will have a higher transaction throughput but this is because it defaults to MVCC SQL Server defaults to blocking selects on uncommitted updates but it can be changed to MVCC as well so that difference should basically go away See Read Committed Isolation Level See Enabling Row Versioning-Based Isolation Levels
postgresql - Disabling MVCC in Postgres - Stack Overflow I've decades of experience with MSSQL but none with Postgres and its MVCC style of concurrency control In MSSQL if I had a very large dataset which was read-only, I would set the database to read-
MySQL Repeatable Read isolation level and Lost Update phenomena Apparently, InnoDB does not work like that shouldn't MySQL MVCC prevent Lost Update using database-level Pessimistic Locking resulting in transaction rollback MVCC does not use any Pessimistic Locking in Repeatable Read The only locks taken are the gap and next-key locks taken on the clustered index, but those don't prevent Lost Updates