Random thoughts on a Friday afternoon…
We’ve all got problems. More to the point, every IT department or team has problems of some kind. It’s why we hire consultants, buy products, start long and arduous journeys into the great unknown depths of root cause analysis, and so on.
What fascinates me is the level at which we come to identify with our problems. When I’ve gone into an environment to deliver recommendations, the conversation usually (more...)
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.
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
Recently while observing AWR reports, I’ve seen a very good example of how average value hides important pattern.
Here is a Workload Comparison section from an AWR diff report (generated with $ORACLE_HOME/rdbms/admin/awrddrpt.sql):
~~~~~~~~~~~~~~~~~~~ 1st Per Sec 2nd Per Sec %Diff 1st Per Txn 2nd Per Txn %Diff
--------------- --------------- ------ --------------- --------------- ------
DB time: 0.6 0.6 1.6 0.0 0.0 -50.0
CPU time: 0.3 0. (more...)
I have learned something new today and this blog post will be (primary) reminder to myself. I am sure that most Oracle DBA’s or Developers are familiar with this trick - so please skip this post if you are one of them :)
My test table will have 1000000 rows with 1000 NULL values for “OBJECT_NAME” column.
Tests are performed on 11gR1 version.
select c.table_name, c.column_name, c.data_type, c.num_nulls,
When you execute an SQL – why there is a difference in Consistent gets on the same set of data for same SQL. For any SELECT query, oracle need to prepare the consistent data in the buffer cache using undo records then forward the data the requesting session as of a specific SCN. Touching any block in buffer cache to prepare the blocks for consistent data is known as Consistent Reads.
In an (more...)
In the Oracle technical universe, it seems that the end of the calendar year is always eventful. First there’s OpenWorld: obviously significant for official announcements and insight into Oracle’s strategy. It’s also the week when many top engineers around the world meet up in San Francisco to catch up over (more...)
Recently I received an email with an simple content:
"It" is slow again :-)
The email explained a package to be slow.
Ok, I started with my "not enough information" reply and an email conversation began.
We are still not ready to identify the problem, but as there is no (more...)
Here are two interesting enhancements in Oracle database 12c PL/SQL. PL/SQL subprogram defined using WITH clause of a subquery – Oracle database 12c allows PL/SQL declaration section in the WITH clause. One can define PL/SQL function or procedure into a WITH clause. Functions declared in the PL/SQL declaration section can (more...)
Today was speaking at HighLoad++ 2013 Moscow. I had two presentation covering deep internals of JVM. One about JIT compilation and other concerning pauseless garbage collection algorithms.
Slide decks are below (in Russian)
Today I was speaking at CEE SECR 2013 at Moscow.
Below is a slide deck from presentation (in Russian)
To no big surprise, the healthcare.gov website went down promptly after being launched. This is the place where people sign up for “Obamacare,” and officials foolhardily insisted that everything was ready for a million visitors. It wasn’t.
Serious websites generally eschew big-bang launches because it is so hard to get (more...)
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...)
Oracle Coherence data grid has a powerful tool for inplace data manipulation - EntryProcessor. Using entry processor you can get reasonable atomicity guarantees without locks or transactions (and without drastic performance fees associated).
One good example of entry processor would be built-in ConditionalPut processor, which will verify certain condition before (more...)
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...)
This is just a pointer post to a tool which I discovered today. It is ORATOP, to monitor databases real time like top of unix flavours. It is pretty much like MOATS (tool from Tanel Poder and Adrian Billington and RAC version by Jagjeet Singh), with a bit better output (more...)
In this post, I would like to share some knowledge about optimizing indexes in Oracle Coherence.
Normally you should not abuse queering features of your data grid and, hence, you are unlikely to ever need to tune indexing/queering (besides choosing which indexes to create). But sometimes, you really need to (more...)
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...)