Скачать или смотреть SQL Server Non Repeatable Reads examples - Part 21

non repeatable read problem.
How to prevent the non repeatable read problem.
The non repeatable read problem: a visual explanation.
A real-world example of the non repeatable read problem.
Why does the non repeatable read problem happen?
How does the non repeatable read problem happen?
How to use the REPEATABLE READ isolation level?
Non repeatable read problem happens when one transaction reads the same data twice and another transaction updates that data in between the first and second read of transaction one.
Repeatable read or any other higher isolation level should solve the non-repeatable read problem.
Both Read Uncommitted and Read Committed transaction isolation levels have the non repeatable reads side effect. Repeatable Read, Snapshot, and Serializable isolation levels does not have this side effect.
non repeatable read problem
read committed isolation level
repeatable read
Fixing non repeatable read concurrency problem : To fix the non-repeatable read problem, set transaction isolation level of Transaction 1 to repeatable read. This will ensure that the data that Transaction 1 has read, will be prevented from being updated or deleted else where by other transactions. This solves the non-repeatable read problem.
Some of the common concurrency problems
Dirty Reads
Lost Updates
Non-repeatable Reads
Phantom Reads
SQL Server provides different transaction isolation levels, to balance concurrency problems and performance depending on our application needs.
Read Uncommitted
Read Committed
Repeatable Read
Snapshot
Serializable