Detailed explanation of Oracle database log types and functions

Detailed explanation of Oracle database log types and functions

Oracle database is a relational database management system, and its log is one of the very important components of the database. Database logs are mainly used to record the operating processes and events within the database management system, and can play a role in data recovery. In Oracle database, there are three main types of logs: archive logs, redo logs, and transaction logs. This article will explain the functions and usage of these three logs in detail, and provide relevant code examples.

1. Archive Log

Archive log is a very important log type in Oracle database. Its main function is to record all operations in the database so that Recover data in the event of database failure. The generation of archive logs requires turning on the archive mode (Archive Mode) in the database, so that the database will copy the log files to the archive directory for recovery when needed.

The SQL statement to turn on the database archive mode is as follows:

ALTER DATABASE ARCHIVELOG;

The SQL statement to turn off the database archive mode is as follows:

ALTER DATABASE NOARCHIVELOG;

2. Redo Log (Redo Log)

Redo log is another important log type in Oracle database. It is mainly used to record all modification operations in the database, including INSERT, UPDATE and DELETE operations. The function of the redo log is to ensure data consistency when a database failure occurs. The data in the redo log can be used to re-execute the modification operation on the database to restore the data.

In Oracle database, redo log files are periodically switched and reused to prevent the log files from becoming too large. You can use the following SQL statement to view the redo log group information in the current database:

SELECT GROUP#, THREAD#, SEQUENCE#, BYTES, MEMBERS
FROM V$LOG;

3. Transaction Log (Transaction Log)

The transaction log records the execution of transactions in the database Log type, mainly used to ensure that transactions in the database are durable, reliable and consistent. The transaction log is generated every time a transaction is committed or rolled back, recording the start and end information of the transaction, as well as modification operations during execution.

In the Oracle database, you can use the following SQL statement to view the transaction log information in the current database:

SELECT COUNT(*)
FROM V$TRANSACTION;

Summary:

The above are the three common logs in the Oracle database Type: archive log, redo log, and transaction log. These logs play a very important role in database management and can ensure the security and consistency of the database. By properly configuring and managing these logs, the normal operation of the database and the integrity of the data can be effectively guaranteed. Hope the above content is helpful to you!

The above is the detailed content of Detailed explanation of Oracle database log types and functions. For more information, please follow other related articles on the PHP Chinese website!