Recent Updates of OraLatencyMap and PyLatencyMap

Topic: This post introduces the latest changes to OraLatencyMap and PyLatencyMap, two custom tools for collecting and displaying Oracle wait event latency details using heatmaps.

OraLatencyMap is a SQL*Plus tool, with a core written in PL/SQL, aimed at studying Oracle random I/O by displaying the latency drill-down of the wait event 'db file sequential read' using heatmaps. The tool can also be used to collect and display event latency histograms for any other Oracle wait (more...)

Wait Event History Sampling, an Experiment in Oracle Performance Analysis

Topic: This post is about a performance analysis technique based on high frequency sampling of wait event history data in Oracle. Two scripts are provided for performing this type of analysis and two example cases are discussed applied to the study random read latency and read workload characterization.

Context: In the context of performance analysis, for example for a study of I/O response time, I want to analyze the flow of all wait events for (more...)

Clusterware 12c and Restricted Service Registration for RAC

Topic: This post is about exploring the mechanisms used by Oracle Clusterware to restrict remote service registration, i.e. the 12c new feature "Restricting Service Registration for Oracle RAC Deployments"

Why is this useful? This improvement of 12c clusterware and listeners over the 11.2 version is useful mainly for security purposes, for example as a measure against TNS poisoning attacks (see also CVE-2012-1675), and it is particularly relevant for (more...)

How to Recover Files from a Dropped ASM Disk Group

Topic: This post describes a few tips and techniques on how to recover ASM files from a dropped disk group and an example of how to 'undrop' an ASM disk group

Context: This research stems from a recent case I have investigated where the data disk group of a test (more...)

UKOUG Tech13, Latency Sudies and Lost Writes

I am looking forward to participating again to the UKOUG annual conference. This year I will present together with my colleague Marcin Blaszczyk on two topics that are follow-up of articles in this blog.
The first talk is: Storage Latency for Oracle DBAs. A presentation about a performance tuning techniques for (more...)

Daylight Saving Time Change and AWR Data Mining

Topic: this article is about a tip for Oracle 11.2 and higher on how to handle DST change when querying directly the AWR repository. In addition a few comments on Perfsheet4, a tool to extract and plot AWR data in Excel.

Introduction: Statspack and more recently AWR reports, (more...)

Getting Started with PyLatencyMap: Latency Heat Maps for Oracle and DTrace

Topic: this is a getting-started article for PyLatencyMap, a performance tool for real-time investigation and troubleshooting of latency data. Contains examples relevant for the Oracle RDBMS and for DTrace.

Getting started

Download the latest version of PyLatencyMap (also available on GitHub). At the time of this writing PyLatencyMap (more...)

PyLatencyMap, a Performance Tool for Latency Data Visualization

Topic: this post is about PyLatencyMap, a performance-oriented tool I have written for command-line drill down of latency data, integrating various data sources (Oracle, DTrace, trace files) into a basic visualization engine.

Motivations: Understanding a performance problem is often about understanding where time is spent. Many of the systems I (more...)

Dtrace Explorations of Oracle Wait Events on Linux

DTrace is a great tool to measure and investigate latency for performance troubleshooting. DTrace is now coming to the Linux platform too and I would like to share a few tests I did with it. The following is meant to be a short technology exploration but hopefully it can also highlight (more...)