How to parse Oracle Database Concepts 12c

This article introduces you how to analyze Oracle Database Concepts 12c, the content is very detailed, interested friends can refer to, hope to be helpful to you.

Transaction Management (Transaction Management)

Oracle database is a multi-user database system, so Oracle database must ensure that user data will not affect each other when multiple users use it together.

Transaction (Transactions)

To put it simply, a transaction is a logical combination of one or more SQL statements that is atomic. Atomicity means that a combination of one or more SQL statements is either committed or rolled back together. It is impossible to have part of the SQL commit and part of the SQL rollback in the combination. Take the simplified bank transfer (100 yuan from A to B) as an example:

1. Subtract 100 yuan from An account

2. Add 100 yuan to the B account

3. Keep a journal

The Oracle database ensures that the above three operations are integrated and either succeed or fail (rollback).

Concurrent (Data Concurrency)

Another requirement for multi-user database systems is the ability to control concurrency. Concurrency here means that multiple users access the same data at the same time.

Concurrency control is an important means to ensure data integrity. If there is no concurrency control, the data may be inaccurate. For example, while one user is updating a row, another user is also updating the row, which may result in incorrect data.

Waiting is a way to enable multiple users to access the same data, but this can lead to a decline in system performance. Oracle database uses locking mechanism (lock) to realize concurrency control. The locking mechanism will be discussed in detail later.

Data consistency (Data Consistency)

The Oracle database provides each user with a view of data consistency, including changes in their own transactions and changes that have been submitted by other users.

Oracle databases always guarantee statement-level read consistency. Data consistency will be discussed in more detail later.

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