最近刚做完SAP归档和数据库重组，数据库重组完后对临时表空间收缩了下，以合理利用资源，步骤如下： 1、建立新的临时表空间 2、切换默认临时表空间为新建的表空间 3、查看所有用户的默认临时表空间是否切换到新的 4、旧表空间下线 5、删除旧临时表空间 6、删
最近刚做完SAP归档和数据库重组，数据库重组完后对临时表空间收缩了下，以合理利用资源，步骤如下：
1、建立新的临时表空间
2、切换默认临时表空间为新建的表空间
3、查看所有用户的默认临时表空间是否切换到新的
4、旧表空间下线
5、删除旧临时表空间
6、删除数据文件
在切换完临时表空间后, 删除旧的临时表空间data file, 发现文件系统仍然没有全部释放出来, 去umount也不行, 后来在关闭数据库后, 空间终于都释放出来了. 这是AIX的一个机制，与WIn有很大区别, 做数据库重组的同学们也注意下.
Explain the ACID properties (Atomicity, Consistency, Isolation, Durability).Apr 16, 2025 am 12:20 AMACID attributes include atomicity, consistency, isolation and durability, and are the cornerstone of database design. 1. Atomicity ensures that the transaction is either completely successful or completely failed. 2. Consistency ensures that the database remains consistent before and after a transaction. 3. Isolation ensures that transactions do not interfere with each other. 4. Persistence ensures that data is permanently saved after transaction submission.
MySQL: Database Management System vs. Programming LanguageApr 16, 2025 am 12:19 AMMySQL is not only a database management system (DBMS) but also closely related to programming languages. 1) As a DBMS, MySQL is used to store, organize and retrieve data, and optimizing indexes can improve query performance. 2) Combining SQL with programming languages, embedded in Python, using ORM tools such as SQLAlchemy can simplify operations. 3) Performance optimization includes indexing, querying, caching, library and table division and transaction management.
MySQL: Managing Data with SQL CommandsApr 16, 2025 am 12:19 AMMySQL uses SQL commands to manage data. 1. Basic commands include SELECT, INSERT, UPDATE and DELETE. 2. Advanced usage involves JOIN, subquery and aggregate functions. 3. Common errors include syntax, logic and performance issues. 4. Optimization tips include using indexes, avoiding SELECT* and using LIMIT.
MySQL's Purpose: Storing and Managing Data EffectivelyApr 16, 2025 am 12:16 AMMySQL is an efficient relational database management system suitable for storing and managing data. Its advantages include high-performance queries, flexible transaction processing and rich data types. In practical applications, MySQL is often used in e-commerce platforms, social networks and content management systems, but attention should be paid to performance optimization, data security and scalability.
SQL and MySQL: Understanding the RelationshipApr 16, 2025 am 12:14 AMThe relationship between SQL and MySQL is the relationship between standard languages and specific implementations. 1.SQL is a standard language used to manage and operate relational databases, allowing data addition, deletion, modification and query. 2.MySQL is a specific database management system that uses SQL as its operating language and provides efficient data storage and management.
Explain the role of InnoDB redo logs and undo logs.Apr 15, 2025 am 12:16 AMInnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.
What are the key metrics to look for in an EXPLAIN output (type, key, rows, Extra)?Apr 15, 2025 am 12:15 AMKey metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.
What is the Using temporary status in EXPLAIN and how to avoid it?Apr 15, 2025 am 12:14 AMUsingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB
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