Diagnostics

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. ...

Oracle SQL Monitor: Real-Time Execution Diagnostics for Long-Running Queries

Oracle SQL Monitor is the most powerful single-query diagnostic tool in the Oracle performance toolkit. Unlike DBMS_XPLAN.DISPLAY_CURSOR, which gives you a static execution plan, SQL Monitor captures real-time runtime statistics at every step of the execution plan — rows processed, memory used, temporary I/O, CPU time, and elapsed time per operation. For parallel queries, it shows the workload distribution across parallel server processes. When SQL Monitor Activates Automatically SQL Monitor begins monitoring a SQL statement automatically when either: ...