Java GC in Numbers – Parallel Young Collection

This is a first articles in series, where I would like to study effect of various HotSpot JVM options on duration of STW pauses associated with garbage collection.

This article will study how number of parallel threads affects duration of young collection Stop-the-World pause. HotSpot JVM has several young GC (more...)

Improving data move on EXADATA V

Wrap-up

This is the last post in this series and I’ll not introduce anything new here, but rather just summarise the changes explained and talk a bit about the value the solution delivers to the organisation.

Let’s first review the situation we faced before implementing the changes.

The cost of writing (more...)

Improving data move on EXADATA IV

Reducing storage requirements

In the last post in this series I talked about how we sped up the move of data from operational to historical tables from around 16 hours down to just seconds. You find that post here.

The last area of concern was the amount of storage this (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...)

Improving data move on EXADATA III

Moving to history tables

In the last post I talked about how we made the speed of actually writing all those log-records much faster. It has to date been so fast that no a single report of a problem has been filed. you find that post here.

Once the data (more...)

Speaking at E4 2013! … and some Exadata Patents good stuff

I’ll be co-speaking with Tyler Muth at E4  and we will be talking about Performance Visualization… some of you may already know that I’m really a big fan of Tableau and just to give you an example on what the tool can do I’ve consolidated all the different viz that (more...)

Improving data move on EXADATA II

Writing log records

The last post in this series introduced the problem briefly. You find that post here.

In this post I’ll talk about the changes made to make that writing of log records fast enough. There were 50 million records that was written. Each of them pretty much in its (more...)

Faster data move on EXADATA I

Introduction

In my work among other things I tune and tweak solutions for EXADATA. Today I’ll write about a big improvement we achieved with a process that moves data from the operational tables to the ones where the history is stored.

This will not be a technical post. While I (more...)

SQL Plan Stability and CBO Statistics Myths Busted

Carlos Sierra:

Since lack of Histograms or freezing CBO Statistics do not guarantee Plan Stability, do not rely on these two myths. If what you are looking for is Plan Stability use then SQL Plan Management available since 11g or SQL Profiles available from 10g.


© Eddie Awad's Blog (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...)

New Version Of XPLAN_ASH Tool – Video Tutorial

A new major release (version 3.0) of my XPLAN_ASH tool is available for download.

You can download the latest version here.

In addition to many changes to the way the information is presented and many other smaller changes to functionality there is one major new feature: XPLAN_ASH now also supports S-ASH, the free ASH implementation.

If you run XPLAN_ASH in a S-ASH repository owner schema, it will automatically detect that and adjust accordingly.

(more...)

Direct Path Reads Again

Note: This post is about diagnosing real life scenario caused by  direct path decision change on 11.2.0.3 which already covered  by Tanel Poder on his awesome Optimizer statistics-driven direct path read decision for full table scans (_direct_read_decision_statistics_driven) post
If you already read and know how to (more...)

Oracle OpenWorld Submissions – The Full Monty

Here one day before deadline, I have entered almost my entire current catalog of presentations for consideration in the Oracle OpenWorld 2013 agenda. One new for this year: “Worst Oracle ADF Project Ever” ;-)

If you would like me to speak at one of your events, the following are the presentations (more...)

ORA-00600: internal error code, arguments: [ktprhtnew6]

While recovering a database, stuck with ORA-00600 and database crashed.  We have an Oracle version 11.1 and were hitting a bug: 8310931 and fixed in 11.2.  The bug says, this problem will happen usually on high number of CPUs while doing transaction recovery.  We got 126 CPU in the DB server.


Errors in file /opt/oracle/diag/rdbms/xxxx/xxx/trace/xxx_smon_29786.trc (incident=120257):

ORA-00600: internal error code, arguments: [ktprhtnew6], [], [], [], [], [], [], [], [], [], [], []
Incident details in: /opt/oracle/diag/rdbms/xxx/xxxx/incident/incdir_120257/xxxx_smon_29786_i120257.trc
Fri Feb 22 22:49:14 2013
Trace dumping is performing id=[cdmp_20130222224914]
Fatal internal error happened while SMON was doing active  (more...)

Oracle on AIX – where’s my cpu time ?

This story begins couple of weeks ago when I was asked to look on performance problem for critical processes before go-live. There were differences between run times between different test systems and between runs with 10046 trace enabled or not.

First of all I started with tracing issue. I have checked server CPU and disk utilization using NMON (tool name is important here). There wasn’t any problem with CPU utilization – or at least this is what I was thinking at that time. Tracing was enabled with level 12 (bind and wait) and it generate 2 GB of trace file (more...)

AWR Analytics and Oracle Performance Visualization with PerfSheet4

Topic: This post describes PerfSheet4, a tool for performance analysis aimed at streamlining access and visualization of Oracle's AWR data. The tool is aimed at DBAs and Oracle performance analysts. PerfSheet4 is a spin off of previous original work by Tanel Poder, rewritten and integrated with additional functionality for AWR analysis and with important changes to the user interface.

Context: There is much information in the counters and metrics of Oracle's AWR that can be of substantial help for troubleshooting and for capacity planning. Besides the standard AWR report, time-based analysis is often very useful. However this type of access is (more...)

11.2.0.3 Strange statistic, large transactions, dirty buffers and “direct path read”

Summary

I recently investigated an IO performance “spike” on a large 11.2.0.3 transactional system and I thought I would cover some interesting issues found. I am going to take the approach of detailing the observations made from our production and test systems and avoid attempting to cover how other versions of Oracle behave. The investigation also uncovers a confusing database statistic which we are currently discussing with Oracle Development so they can decide if this is an Oracle coding bug or a documentation issue.

The initial IO issue

We run a simple home grown database monitor which watches database wait events and sends an email alert if it detects either a (more...)

DTrace is now also available for Oracle Linux

Uncategorized
| Dec 31, 2012

Oracle has ported DTrace for Oracle Linux. DTrace is a very powerful performance analysis and troubleshooting tool that allows you to instrument all software. It’s name is short for Dynamic Tracing. I’m not a DTrace expert but some say it is that powerful that it allows you to reverse engineer any software…


Filed under: Oracle, Performance

Coherence 101, Beware of cache listeners

Cache events facility is a quite useful feature of Oracle Coherence. For example, continuous queries and near cache features are build on top of cache event system.
Unfortunately it could be also abused easily. In particular, they are noticeably bad at scale unless you are very careful.
Please note. This (more...)

Total Time and Bits of Time

Our Experience Tells Us So...

We know from hard-fought experience that the more work we push through a system the more processing time involved. That's not rocket science... but to mathematically represent the relationship between work and time is rocket science.

Decades ago Operations Research queuing theory researchers quantitatively established the relationship between work and time. They put into math what we all have experienced. In our DBA world this means that as the system activity increases, then so does CPU consumption and eventually Oracle non-idle wait time.

Find The Big Bar

The classic way to graphically represent all the (more...)