DBA AWR Wait Class by Time
Description:
Non idle session wait times by wait class over time. Each row shows the system-wide wait time per wait class of one AWR snapshot interval to identify unusual wait events that occured at specific times. Use the Session Type parameter to restrict either to foreground, background or all server processes.
To see data in this report based on dba_hist_system_event, set the following: alter session set container=PDB1; alter system set awr_pdb_autoflush_enabled=true;
https://www.enginatics.com/blog/updated-dba-awr-blitz-reports-now-work-with-plugglable-databases/
Parameters
Date From, Date To, Session Type, Diagnostic Pack enabled, Container Data
Used tables
dba_hist_snapshot, dba_hist_system_event
Categories
Related reports
Dependencies
If you would like to try one of these Oracle EBS SQLs without having Blitz Report installed, note that some of the reports require functions from utility package xxen_util.
Example Report
DBA AWR Wait Class by Time 22-Dec-2025 083647.xlsx
Report SQL
www.enginatics.com/reports/dba-awr-wait-class-by-time/
Blitz Report™ import options
DBA_AWR_Wait_Class_by_Time.xml
Executive Summary
This report provides a comprehensive analysis of non-idle session wait times categorized by wait class over a specified time range. It is a critical tool for Database Administrators (DBAs) to identify system-wide performance bottlenecks and understand the distribution of database time across different activity types such as I/O, Concurrency, or Application logic.
Business Challenge
- Performance Degradation: Difficulty in pinpointing the exact time periods when database performance suffers.
- Root Cause Analysis: Challenges in distinguishing between I/O-bound, CPU-bound, or contention-related issues.
- Capacity Planning: Lack of historical data trends to forecast future resource requirements.
The Solution
The DBA AWR Wait Class by Time Blitz Report addresses these challenges by:
- Time-Series Visualization: Presenting wait class data per AWR snapshot interval, allowing for precise correlation with reported slow periods.
- Drill-Down Capabilities: Enabling users to isolate specific wait classes (e.g., “User I/O”) to see their impact over time.
- Pluggable Database Support: Fully compatible with Oracle Multitenant architecture, allowing analysis at the PDB level.
Technical Architecture
The report queries the Oracle Automatic Workload Repository (AWR) tables, specifically DBA_HIST_SNAPSHOT and DBA_HIST_SYSTEM_EVENT. It aggregates the TIME_WAITED_MICRO metric by WAIT_CLASS for each snapshot interval. The logic handles the delta calculation between snapshots to show the wait time incurred during each specific interval rather than cumulative totals.
Parameters & Filtering
- Date From / Date To: Defines the time window for the analysis.
- Session Type: Filters data for ‘Foreground’, ‘Background’, or ‘All’ sessions. Foreground is typically most relevant for user experience.
- Container Data: For multitenant environments, allows selection of specific containers.
Performance & Optimization
- Date Range: Keep the date range focused (e.g., 1-2 days) for high-resolution analysis, as AWR data can be voluminous.
- Snapshot Interval: Ensure AWR snapshot intervals are appropriate (typically 15-60 minutes) for the level of granularity required.
FAQ
- Q: Why do I see no data for my PDB?
- A: Ensure that
awr_pdb_autoflush_enabledis set totrueand you are connected to the correct container.
- A: Ensure that
- Q: What is “DB CPU”?
- A: While not a “wait class” in the traditional sense, this report often includes CPU time to provide a complete picture of DB time.
Oracle E-Business Suite Reporting Library
We provide an open source Oracle EBS SQLs as a part of operational and project implementation support toolkits for rapid Excel reports generation.
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