Common scenarios and solutions for table locking in Oracle databases
Common scenarios and solutions for table locking in Oracle database
In Oracle database, table locking is a common database performance problem. When multiple sessions access it at the same time, When using the same table, it may cause the table to be locked, thus affecting the performance and stability of the system. This article will discuss some common table locking scenarios and provide corresponding solutions and code examples.
- Scenario 1: Long-term transactions cause table locks
This scenario usually occurs when a long-term lock is occupied during the execution of a session. table, causing other sessions to be unable to operate on the table. To solve this problem, you can release the table lock by finding the long-running transaction and aborting it. The following is a sample code:
SELECT SID, SERIAL#, SQL_ID, STATUS FROM V$SESSION WHERE STATUS = 'ACTIVE' AND SQL_ID IS NOT NULL ORDER BY LAST_CALL_ET DESC; ALTER SYSTEM KILL SESSION 'SID,SERIAL#';
- Scenario 2: Concurrent updates cause table locks
When multiple sessions try to update the same row of data at the same time , row-level locks may occur causing table locks. To avoid this situation, you can use row-level locks or add appropriate waiting times to your code. The following is a sample code:
SELECT * FROM table_name WHERE column_name = 'value' FOR UPDATE;
- Scenario 3: DDL operation causes table lock
When a session performs a DDL operation (such as ALTER TABLE , DROP TABLE, etc.), the entire table may be locked, preventing other sessions from operating on the table. To solve this problem, you can perform DDL operations during non-working hours and enable DDL locks when necessary. The following is a sample code:
LOCK TABLE table_name IN EXCLUSIVE MODE;
- Scenario 4: Table lock caused by index
If a query does not use the index correctly, it may cause Table level locking. To avoid this situation, you can optimize the query statement to use the correct index. The following is a sample code:
CREATE INDEX index_name ON table_name(column_name);
Summary:
Table locking is a common performance problem in Oracle databases, but by understanding common locking scenarios and corresponding solutions, we can effectively avoid them Or resolve table locking issues. In practical applications, it is necessary to select the appropriate solution according to the specific situation, and adjust and optimize it according to the actual situation to ensure the stability and performance of the system.
(Note: The above code is for reference only, please adjust and test according to the actual situation.)
The above is the detailed content of Common scenarios and solutions for table locking in Oracle databases. For more information, please follow other related articles on the PHP Chinese website!

MySQLoffersvariousstorageengines,eachsuitedfordifferentusecases:1)InnoDBisidealforapplicationsneedingACIDcomplianceandhighconcurrency,supportingtransactionsandforeignkeys.2)MyISAMisbestforread-heavyworkloads,lackingtransactionsupport.3)Memoryengineis

Common security vulnerabilities in MySQL include SQL injection, weak passwords, improper permission configuration, and unupdated software. 1. SQL injection can be prevented by using preprocessing statements. 2. Weak passwords can be avoided by forcibly using strong password strategies. 3. Improper permission configuration can be resolved through regular review and adjustment of user permissions. 4. Unupdated software can be patched by regularly checking and updating the MySQL version.

Identifying slow queries in MySQL can be achieved by enabling slow query logs and setting thresholds. 1. Enable slow query logs and set thresholds. 2. View and analyze slow query log files, and use tools such as mysqldumpslow or pt-query-digest for in-depth analysis. 3. Optimizing slow queries can be achieved through index optimization, query rewriting and avoiding the use of SELECT*.

To monitor the health and performance of MySQL servers, you should pay attention to system health, performance metrics and query execution. 1) Monitor system health: Use top, htop or SHOWGLOBALSTATUS commands to view CPU, memory, disk I/O and network activities. 2) Track performance indicators: monitor key indicators such as query number per second, average query time and cache hit rate. 3) Ensure query execution optimization: Enable slow query logs, record and optimize queries whose execution time exceeds the set threshold.

The main difference between MySQL and MariaDB is performance, functionality and license: 1. MySQL is developed by Oracle, and MariaDB is its fork. 2. MariaDB may perform better in high load environments. 3.MariaDB provides more storage engines and functions. 4.MySQL adopts a dual license, and MariaDB is completely open source. The existing infrastructure, performance requirements, functional requirements and license costs should be taken into account when choosing.

MySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.

The situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.

In MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

Dreamweaver CS6
Visual web development tools

SublimeText3 Linux new version
SublimeText3 Linux latest version

SublimeText3 Chinese version
Chinese version, very easy to use
