For further deep dives, refer to the official Oracle Database 12c Release 2 Performance Tuning Guide (Oracle Press, ISBN: 978-1-259-83765-4). The techniques above are tested on Oracle Database 12.2.0.1 and later.
SELECT COUNT(DISTINCT user_id) FROM web_hits WHERE hit_date = SYSDATE; For further deep dives, refer to the official
The book provides actionable methods for optimizing various database layers: SQL & Adaptive Tuning : Features in-depth coverage of Adaptive Query Optimization Adaptive Statistics , and automated tools like the SQL Tuning Advisor SQL Performance Analyzer (SPA) Storage & I/O : Covers strategies for avoiding disk contention using partitions Bigfile Tablespaces ASM (Automatic Storage Management) . It also details the 12c Heat Map Automatic Data Optimization (ADO) Memory Management : Provides techniques for tuning the Shared Pool Buffer Cache , as well as leveraging Automatic Memory Management Index Optimization : Explores advanced methods like Advanced Index Compression It also details the 12c Heat Map Automatic
In 12.1, SQL Plan Directives were often the root cause of sudden plan changes. 12.2 introduced automatic maintenance to purge stale directives. However, you should manually review: you should manually review: