What does transaction consistency mean?

The consistency of a transaction means: the transaction must change the database from one consistency state to another consistency state. In order to ensure the correct execution of transactions and maintain the integrity of the database, transactions must have the following characteristics: atomicity, consistency, isolation and durability.

The consistency of a transaction means that the transaction must change the database from one consistency state to another consistency state.

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Analysis:

In order to ensure the correct execution of transactions and maintain the integrity of the database, transactions Must have the following properties: atomicity, consistency, isolation, and durability. Consistency refers to the isolated execution of transactions (without other concurrent transactions) to maintain the consistency of the database.

Detailed introduction:

Properties:

1. Atomicity: All operations in the transaction are indivisible in the database, either all are completed, or all Not executed.

2. Consistency: The execution results of several transactions executed in parallel must be consistent with the results of serial execution in a certain order.

3. Isolation: The execution of a transaction is not interfered with by other transactions, and the intermediate results of transaction execution must be transparent to other transactions.

4. Durability: For any submitted transaction, the system must ensure that the changes to the database made by the transaction are not lost, even if the database fails.

The ACID characteristics of transactions are implemented by relational database systems (DBMS). DBMS uses logs to ensure the atomicity, consistency and durability of transactions.

The log records the updates made by the transaction to the database. If an error occurs during the execution of a transaction, the updates made by the transaction to the database can be revoked based on the log, so that the database can be rolled back to the initial state before the transaction was executed. state.

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