"Discussion on Oracle Log Classification and Optimization Strategies"

In the Oracle database, log files are a very important component, which records the activities and changes of the database. Ensure data integrity and consistency. For database administrators, it is very critical to effectively manage and optimize database logs to improve database performance and stability. This article will discuss the classification and optimization strategies of logs in Oracle database, and give relevant code examples.

1. Classification of Oracle logs

In the Oracle database, there are three main types of logs: archive log (Archive log), online redo log (Redo log) and log audit log ( Audit log). The functions and characteristics of these three logs will be introduced below.

1. Archive log(Archive log)

Archive log is a very important log type in Oracle database. It records all modification operations of the database, including data modification operations. Insert, update and delete etc. The main function of the archive log is for database recovery and backup. When the database fails, the data can be restored based on the archive log.

Create archive log:

ALTER DATABASE ARCHIVELOG;

View archive log status:

SELECT LOG_MODE FROM V$DATABASE;

2. Online redo log (Redo log)

Online Redo log is an important means for Oracle database to ensure the durability and consistency of transactions. It records the changes of transactions and can be used for database recovery and rollback operations. Online redo logs are written cyclically. When a redo log file is full, it will be continued to be used or archived.

View the status of the redo log group:

SELECT GROUP#, STATUS FROM V$LOG;

Adjust the redo log file size:

ALTER DATABASE ADD LOGFILE GROUP 4 ('/u01/redologs/redo04a.log','/u01/redologs/redo04b.log') SIZE 50M;

3. Log audit log (Audit log)

Log Audit log is used to record the audit log of database user operations, including login information, DDL operations, DML operations, etc. Audit logs can be used to track records of database operations to ensure database security and compliance.

Enable audit function:

AUDIT ALL BY SYS BY ACCESS;

View audit records:

SELECT * FROM DBA_AUDIT_TRAIL;

2. Oracle log optimization strategy

In daily database management work, we need Consider how to optimize the database's logging function to improve database performance and efficiency. The following are some common Oracle log optimization strategies:

1. Reasonably configure the size and number of log files

Reasonably configure the size and number of archive logs and redo logs to avoid log Files that are too large or too small cause performance issues. It is generally recommended to set a smaller log file size to ensure that frequently submitted transactions can be written to the log file quickly.

2. Separate redo logs of hotspot tables

If there is a hotspot table in the database, you can consider setting a separate redo log group for the table to avoid update operations of the hotspot table Affects the IO performance of other tables.

3. Enable log compression function

Oracle database provides a log compression function, which can compress and store redo logs to reduce disk space usage. Turning on the log compression function can improve the IO performance of the database.

ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE '/u01/change_tracking/change_tracking.f';

4. Regularly clean up expired archive logs

Regularly clean up expired archive logs in the database to avoid log files taking up too much disk space. You can write scheduled tasks or scripts to automatically clean up expired archive logs in the database.

rman target / <<EOF
DELETE ARCHIVELOG ALL COMPLETED BEFORE 'SYSDATE-7';
EOF

5. Use fast log group switching

Fast log group switching is an optimization strategy in Oracle database that can reduce the performance loss caused by redo log group switching . When frequent redo log group switching is performed, consider enabling fast log group switching to improve database performance.

ALTER DATABASE FORCE LOGGING;

Through the above discussion, we have learned about the classification and optimization strategies of logs in Oracle database, and given relevant code examples. Properly managing and optimizing the log function of the database is very important to improve the performance and stability of the database. I hope the above content will be helpful to you.

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