在归档日志模式下,有可能会遇到归档日志大小超过最大值而出现讨厌的ORA-00257错误,前面说了如何把归档日志空间变大。而在普通的
在归档日志模式下,有可能会遇到归档日志大小超过最大值而出现讨厌的ORA-00257错误,,前面说了如何把归档日志空间变大。而在普通的开发环境下,其实是根本用不着归档日志的,设个时候我们就把数据库的归档日志给禁用了,也就是说把数据库变为非归档日志模式,应该怎么做呢。
在这里所有的操作要在数据库的那台机器上操作,用SYS用户进行登录,首先设置归档进程关闭。
alter system set log_archive_start=false scope=spfile;
然后关闭数据库
shutdown immediate
再后面把数据库启动到mount的模式
startup mount
关闭flash闪回数据库模式,如果不关闭的话,在后面关闭归档日志的时候就会出现讨厌的ORA-38774错误。
alter database flashback off
接着把数据库改为非归档模式
alter database noarchivelog;
都修改好了以后,然后打开数据库
Alter database open;
察看一下归档日志的空间大小
select * from v$recovery_file_dest;
接着看一下log日志的状态
select * from v$log;
再看一下闪回日志使用状况
select * from v$flash_recovery_area_usage;

The steps to create and manage user accounts in MySQL are as follows: 1. Create a user: Use CREATEUSER'newuser'@'localhost'IDENTIFIEDBY'password'; 2. Assign permissions: Use GRANTSELECT, INSERT, UPDATEONmydatabase.TO'newuser'@'localhost'; 3. Fix permission error: Use REVOKEALLPRIVILEGESONmydatabase.FROM'newuser'@'localhost'; then reassign permissions; 4. Optimization permissions: Use SHOWGRA

MySQL is suitable for rapid development and small and medium-sized applications, while Oracle is suitable for large enterprises and high availability needs. 1) MySQL is open source and easy to use, suitable for web applications and small and medium-sized enterprises. 2) Oracle is powerful and suitable for large enterprises and government agencies. 3) MySQL supports a variety of storage engines, and Oracle provides rich enterprise-level functions.

The disadvantages of MySQL compared to other relational databases include: 1. Performance issues: You may encounter bottlenecks when processing large-scale data, and PostgreSQL performs better in complex queries and big data processing. 2. Scalability: The horizontal scaling ability is not as good as Google Spanner and Amazon Aurora. 3. Functional limitations: Not as good as PostgreSQL and Oracle in advanced functions, some functions require more custom code and maintenance.

MySQL supports four JOIN types: INNERJOIN, LEFTJOIN, RIGHTJOIN and FULLOUTERJOIN. 1.INNERJOIN is used to match rows in two tables and return results that meet the criteria. 2.LEFTJOIN returns all rows in the left table, even if the right table does not match. 3. RIGHTJOIN is opposite to LEFTJOIN and returns all rows in the right table. 4.FULLOUTERJOIN returns all rows in the two tables that meet or do not meet the conditions.

MySQL's performance under high load has its advantages and disadvantages compared with other RDBMSs. 1) MySQL performs well under high loads through the InnoDB engine and optimization strategies such as indexing, query cache and partition tables. 2) PostgreSQL provides efficient concurrent read and write through the MVCC mechanism, while Oracle and Microsoft SQLServer improve performance through their respective optimization strategies. With reasonable configuration and optimization, MySQL can perform well in high load environments.

InnoDBBufferPool reduces disk I/O by caching data and indexing pages, improving database performance. Its working principle includes: 1. Data reading: Read data from BufferPool; 2. Data writing: After modifying the data, write to BufferPool and refresh it to disk regularly; 3. Cache management: Use the LRU algorithm to manage cache pages; 4. Reading mechanism: Load adjacent data pages in advance. By sizing the BufferPool and using multiple instances, database performance can be optimized.

Compared with other programming languages, MySQL is mainly used to store and manage data, while other languages such as Python, Java, and C are used for logical processing and application development. MySQL is known for its high performance, scalability and cross-platform support, suitable for data management needs, while other languages have advantages in their respective fields such as data analytics, enterprise applications, and system programming.

MySQL is worth learning because it is a powerful open source database management system suitable for data storage, management and analysis. 1) MySQL is a relational database that uses SQL to operate data and is suitable for structured data management. 2) The SQL language is the key to interacting with MySQL and supports CRUD operations. 3) The working principle of MySQL includes client/server architecture, storage engine and query optimizer. 4) Basic usage includes creating databases and tables, and advanced usage involves joining tables using JOIN. 5) Common errors include syntax errors and permission issues, and debugging skills include checking syntax and using EXPLAIN commands. 6) Performance optimization involves the use of indexes, optimization of SQL statements and regular maintenance of databases.


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