Oracle SGA Tuning Best Practices

ORACLE学习书籍，英文版的，看书名就知道是关于PL/SQL练习的书，可以尝试一下。

In Oracle, new plans are not used unless they have been validated. The DBA can validate plans at any time or schedule validation during the maintenance window. The optimizer checks if the new plan is equal to or better than the old one. Statement log and Plan history play key roles in the process. If the new plan is as good as or better than the old one, it is added to the plan baseline. Plans that do not perform as well are stored in plan history and marked as unaccepted. During validation, multiple baselines can be tested and the one with the lowest cost will be chosen. This process is particularly useful for volatile tables and cursor sharing scenarios. By default, the retention period for baselines is 53 weeks.

Oracle DBA is a complex system that requires precise configuration and tuning to ensure database security and performance. This article covers multiple aspects of Oracle DBA adjustment and optimization, including password management, performance tuning, log management, and storage management. 1. Password Management is a critical aspect of Oracle DBA, as the security of passwords directly impacts the overall database security. By default, database user passwords expire after 180 days. To prevent this, you can adjust the PASSWORD_LIFE_TIME parameter to control the lifespan of passwords. 1.1 Adjusting PASSWORD_LIFE_TIME: The PASSWORD_LIFE_TIME parameter controls the lifespan of passwords, which is set to 180 days by default. Adjusting this parameter ensures that passwords remain valid without causing database connection issues due to expiration. 2. Performance Tuning is key to maintaining database efficiency. Proper performance tuning can significantly improve the response time and throughput of the database. 1.2 Setting Dump File Size Limit: The size of dump files directly impacts database performance. Setting an appropriate limit for dump file size can enhance database performance. 1.3 Adjusting Default Partition Size: Default partition size adjustments can affect database performance. A reasonable partition size will help improve response time. 1.4 Disabling Automatic Undo Retention Adjustment: Disabling this feature can help optimize database performance. 1.5 Setting Parallel Process Limits: The number of parallel processes directly affects performance. Proper limits can improve database responsiveness. 1.6 Controlling the Retention Time of Control Files: Adjusting control file retention times enhances database security. 1.7 Disabling Delayed Initialization of Extents in 11g: Disabling delayed extent initialization can improve performance. 1.8 Disabling Result Cache: Turning off the result_cache improves performance by reducing resource consumption. 1.9 Disabling Login/Logout Auditing: Disabling login and logout auditing can significantly improve database performance. 1.10 Adjusting AWR Retention Time: Proper AWR retention time helps in optimizing database performance. 1.11 Disabling Adaptive Cursor Sharing: Turning off adaptive cursor sharing will reduce resource consumption and enhance performance. 1.12 Disabling Cardinality Feedback: Disabling cardinality feedback helps improve performance and reduce resource usage. 1.13 Configuring Events 28401 and 10949: Configuring these events can affect database performance and efficiency."

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This document outlines best practices for implementing continuous data protection for MySQL databases, illustrated by a case study of the .IE registry's restore process. Best Practices: Regular Backups: Implement a robust backup strategy encompassing full, incremental, and potentially log-based backups to minimize data loss. Backup Validation: Regularly test backups to ensure their recoverability and completeness. Point-in-Time Recovery: Implement mechanisms for point-in-time recovery to restore data to a specific timestamp. Redundancy and Replication: Utilize replication technologies to maintain redundant copies of data and ensure high availability. Disaster Recovery Planning: Develop and regularly test a comprehensive disaster recovery plan that includes backup restoration procedures. .IE Continuous Restore Process: The .IE registry's restore process serves as a case study for continuous data protection. Key elements include: Automated Backups: Automated, frequent backups ensure minimal data loss. Offsite Storage: Secure offsite storage protects backups from local disasters. Regular Testing: Routine testing validates the recoverability of backups. Documented Procedures: Clearly documented procedures streamline the restore process. Benefits: Minimized Data Loss Reduced Downtime Enhanced Data Integrity Improved Disaster Recovery Posture Conclusion: Implementing continuous data protection for MySQL databases is crucial for maintaining data integrity and availability. By adhering to best practices and learning from real-world examples, organizations can significantly reduce the risks associated with data loss and ensure business continuity.

大数据系统构建 在可扩展实时数据系统的构建中，理解其原理和最佳实践至关重要。1. 架构设计: 采用微服务架构，以支持横向扩展。2. 数据流处理: 利用流处理框架，如Apache Kafka或Apache Flink，确保数据的实时性。3. 存储方案: 选择适合的存储技术，如NoSQL数据库，以满足高并发和大数据量的需求。4. 监控与优化: 定期进行系统性能的监控，并对数据处理过程进行优化，确保系统的稳定性与高效性。

为作者基于ORACLE官方文档的学习总结，详细介绍了ORACLE中SGA（共享全局区）的基本概念及其内存分配原则。

Chapter 1: Oracle SQL Tuning Pocket ReferenceSection 1.1: IntroductionSection 1.2: The SQL OptimizersSection 1.3: Rule-Based Optimizer Problems and SolutionsSection 1.4: Cost-Based Optimizer Problems and SolutionsSection 1.5: Problems Common to Rule and Cost with SolutionsSection 1.6: Handy SQL Tuning TipsSection 1.7: Using SQL HintsSection 1.8: Using DBMS_STATS to Manage StatisticsSection 1.9: Using Outlines for Consistent Execution Plans

系统全局区（SGA）是Oracle数据库中的关键组成部分，包括共享池、数据库高速缓存、重做日志缓存等内存结构。SGA的大小可以通过动态调整而不需要关闭实例，这使得数据库缓冲区、共享池和大池的大小能够根据工作负载自动调整，最大可达SGA_MAX_SIZE。确定SGA大小的关键参数包括DB_CACHE_SIZE和SGA_MAX_SIZE。