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...)
"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...)
As usual the latest version can be downloaded here.
The new version comes with numerous improvements and (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)
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...)
IMU and Private strands are interesting new entries in Oracle 10g. These to private buffer to a transaction will help to avoid many expensive latches both in buffer cache and log buffer. There are tons of data available in the net about these subjects and many experts spoke (more...)
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).
SJK is small command line tool implementing number of helpful commands for JMV troubleshooting. Internally SJK is using same diagnostic APIs as standard JDK tools (e.g. jps, jstack, jmap, jconsole).
Recently I've made few noteworthy additions to SJK package and would like to announce them here.
Memory allocation rates (more...)
Motivations: Understanding a performance problem is often about understanding where time is spent. Many of the systems I (more...)
session_cached_cursors is one of the neglected parameter in oracle environment which specifies the number cursor cached in the PGA of a session. Any SQL executed multiple times will be cached and executed with a softer soft parsing. There can be 3 scenarios for any parse request.
SQL parsing (more...)
Compressed OOPs (OOP – ordinary object pointer) is a technique reducing size of Java object in 64 bit environments. HotSpot wiki has a good article explaining details. Downside of this technique is what address uncompressing is required before accessing memory referenced by compressed OOPs. Instruction set (e.g. x86) may (more...)
Got a question: What will happen a running curosr got invalidated? SQL execution will fail or invalidation is not at all possible?
There are two components for an executing cursor. A session cached cursor (private area where row source are getting processed) in PGA and sharable execution plan (shared excution (more...)
Today was speaking at Oracle Coherence SIG at London.
Below you can find slide deck from my presentation.