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This article mainly introduces what are the data inconsistencies caused by concurrent operations, which can be used for reference. I hope you can learn a lot after reading this article. Let's take a look at it.

There are three types of data inconsistencies caused by concurrent operations: missing modifications, non-repeatable reading and reading "dirty" data. The method and technology to avoid inconsistency is concurrency control, and the most commonly used technology is blocking technology; other technologies can also be used, such as timestamp method can be used for concurrency control in distributed database systems.

There are three types of data inconsistencies caused by concurrent operations: missing modifications, non-repeatable reading and reading "dirty" data.

1. Lost modification (Lost Update)

Two transactions T1 and T2 read the same data and modified, and the result of T2 commit destroyed (overwritten) the result of T1 commit, resulting in T1 modification being lost.

2. Non-repeatable (Non-Repeatable Read)

Non-repeatable read means that after transaction T1 reads data, transaction T2 performs an update operation so that T1 cannot reproduce the result of the previous read.

3. Read "dirty" data (Dirty Read)

Reading "dirty" data means that transaction T1 modifies a certain data and writes it back to disk. After transaction T2 reads the same data, T1 is revoked for some reason, at this time, the modified data of T1 is restored, and the data read by T2 is inconsistent with the data in the database, then the data read by T2 is "dirty" data, that is, incorrect data.

What can be done to avoid all kinds of inconsistencies?

The method and technology to avoid inconsistency is concurrency control, and the most commonly used technology is blocking technology; other technologies can also be used, such as timestamp method can be used for concurrency control in distributed database systems.

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