Wait-Events

Reading an Exadata AWR Report: A Full Case Study from Symptom to Root Cause

AWR reports are simultaneously the most powerful and most misread performance tool in Oracle’s arsenal. Most DBAs jump straight to Top SQL, copy the SQL_ID, and start tuning — skipping the sections that tell them why that SQL became a problem in the first place. This case study walks through a realistic AWR from a production Exadata system, section by section, using a deliberately constructed problematic scenario. Every number is fabricated for illustrative purposes; every diagnostic conclusion is grounded in real Oracle internals. ...

AWR and ASH Analysis Methodology: A Structured Approach to Oracle Performance Diagnostics

Performance diagnostics without a methodology is archaeology — you dig until you find something interesting, not necessarily something important. Oracle’s AWR and ASH provide an extraordinarily detailed record of database activity, but interpreting them requires a structured approach. This article presents a top-down methodology that moves from macro to micro: DB Time → Wait Profile → Top SQL → Root Cause. The Foundation: DB Time DB Time is the total time all sessions spent working in the database (on CPU or waiting for database resources) during a snapshot period. It is the single most important number in the AWR report. ...

Oracle Performance Tuning Scripts: Real-World Scenarios for CDB and Single Instance

This article is a practical tuning script library. Each script targets a specific, common real-world performance scenario — not abstract examples, but the situations that actually appear at 2am during an incident. Scripts are annotated with where they run, what the output means, and what action to take. Reference Environment Single Instance: Host: ora19c01.prod.example.com DB Name: ORCL19C Oracle: 19.22.0.0 (Oracle Linux 8) Memory: 256 GB RAM, 32 vCPU Storage: Local NVMe (non-Exadata) CDB Environment: Host: cdb01.prod.example.com (Exadata VM) CDB Name: PRODCDB PDBs: PDB_OLTP, PDB_DWH, PDB_REPORTING Oracle: 19.22.0.0 Memory: 512 GB RAM (Exadata X8M-2 node) Scenario 1: “The Database Was Slow from 09:00 to 09:30 This Morning” Situation: Application team reports intermittent slowness on cdb01. You need to identify what happened between 09:00 and 09:30. ...