版本 11.2.0.1.0rac1 rac2 linux 5.3U 2.6.18-128.el5 因为要修复一个bug做测试,在一个节点上修改隐含参数,然后重启!在测
版本 11.2.0.1.0
rac1
rac2
linux 5.3U 2.6.18-128.el5
因为要修复一个bug做测试,在一个节点上修改隐含参数,,然后重启!在测试的过程中遇到
修改了rac1 上的参数
sys@rac1>alter system set "_gc_read_mostly_locking"=false scope=spfile sid='rac1';
sys@rac1>shutdown immedate
Database closed.
Database dismounted.
Oracle instance shut down.
在启动的时候遇到如下报错:
sys@rac1> startup
ORACLE instance started.
Total System Global Area 1653518336 bytes
Fixed Size 2213896 bytes
Variable Size 1275070456 bytes
Database Buffers 369098752 bytes
Redo Buffers 7135232 bytes
ORA-01105: mount is incompatible with mounts by other instances
ORA-01606: parameter not identical to that of another mounted instance
报警日志中
ALTER DATABASE MOUNT
NOTE: Loaded library: /opt/oracle/extapi/64/asm/orcl/1/libasm.so
NOTE: Loaded library: System
SUCCESS: diskgroup DATA2 was mounted
NOTE: dependency between database rac and diskgroup resource ora.DATA2.dg is established
ORA-1105 signalled during: ALTER DATABASE MOUNT...
Sun Jul 01 19:17:49 2012
Starting ORACLE instance (normal)
因为节点1 和节点2 上面 _gc_read_mostly_locking 参数不一样,导致上面的错误。
解决办法:
因为节点2没有关闭,所以在节点上执行
sys@rac2>alter system set "_gc_read_mostly_locking"=false scope=spfile sid='*';
再次启动rac1 的数据库 就可以成功启动!
拓展一下,如果修改隐含参数的时候sid指定为*,重启一个节点 是ok的!
sys@rac1>alter system set "_gc_read_mostly_locking"=false scope=spfile sid='*';
System altered.
sys@rac1>shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
sys@rac1>startup
ORACLE instance started.
Total System Global Area 1653518336 bytes
Fixed Size 2213896 bytes
Variable Size 1275070456 bytes
Database Buffers 369098752 bytes
Redo Buffers 7135232 bytes
Database mounted.
Database opened.
sys@rac1>

InnoDB 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.

Key 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.

Usingtemporary 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

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

SublimeText3 Chinese version
Chinese version, very easy to use

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

WebStorm Mac version
Useful JavaScript development tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment