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...)

OraLatencyMap v1.1 and Testing with SLOB 2

Topic: OraLatencyMap v1.1 is an updated versions of a performance tool aimed at collecting and displaying Oracle wait event histogram data as latency heat maps. We will also briefly discuss an example of the usage of OraLatencyMap in the context of storage testing.

OraLatencyMap v1.1 is now available (more...)

Latency Heat Maps in SQL*plus with OraLatencyMap

Topic: This post is about the use of heat maps to investigate wait event latency in Oracle (and in particular I/O-related latency). This post also discusses a SQL*plus-based script/tool I have developed to help with this type of monitoring and performance drill-down (OraLatencyMap).

Context: Oracle (since version 11gR1) exposes (more...)

Testing Lost Writes in Oracle and with Data Guard

Topic: This post is about lost writes in Oracle and in particular on techniques to reproduce and investigate the effects of lost writes in a test environment and with Data Guard

Motivations: Imagine this scenario: a production system has two standbys to protect against disaster and to load balance read-only load (with (more...)