Recently a customer called us that there is something wrong after upgrading Oracle Database to 19.15 on RedHat. Apparently The amount of RAM consumed by DBWR and process servers became really impressive – as a proof I got screenshots looking like this: They said that before the migration it never looked like this and asked […]
Remember my post, regarding dumping the SGA to read encrypted blocks? What if I tell you, that you can do the same, while being a KVM host administrator with no credentials to a VM itself? Let’s prepare our secure database in a way I did in article AMM vs security. After enabling Oracle Wallet and […]
So apparently this cloud-thing is here for good. You may even say that it became endemic 😉 With cloud there is one potential problem – the bigger and heavier it is, the more possible is the leak. Cloud after all is just a virtualization in a big scale and if you go to public cloud […]
In my previous post I described a case of "enq: TX – row lock contention" that was actually a network latency problem. More and more those kinds of problems (it seems like history happens all over again) caused my friend (Radosław Kut) and me to write a simple tool to analyze SQL performance from a […]
At Trivadis Performance Days 2018 (awesome event by the way) I promised to deliver ODBV3 with support for ASM – and here it is! 🙂 https://github.com/ora600pl/odbv To use it, you have to have access to a user at ASM level with at least SYSDBA privilege. In the connect string you don’t have to add AS […]
It has been crazy few months – organizing POUG2018 took a lot of energy but it was satisfying as hell! 😀 This weekend I had some time to prepare a new version of ODBV for Trivadis Performance Days 2018 where I’ll be talking about the internals of database block storage. The series of articles about […]
After my last article AMM vs security, Martin Berger wrote to me: well, even without AMM you can do it: write your own process which attaches to the same shm segments – and use its memory mapping (?) My response was that it is also possible with ASMM but AMM makes it extremely easy. And […]
Most of us already know that AMM sucks. But usually, we think about disadvantages of AMM in terms of performance. Let’s see why it sucks in the terms of security 😉 Let’s create an encrypted tablespace for HR.EMPLOYEES and protect HR schema with Database Vault. Contents of sqlnet.ora Now we will use dbca to configure […]
In my last blog post I explained a XOR alghorithm that is used to count Oracle database block checksum. I also wrote, that sometimes you are facing problems, that are unresolvable without a low-level knowledge. This is the story of this kind of situation. The story of misread documentation. The story of haste and hex. […]
Recently I’ve started to write my own clone of BBED to have something handy and useful in extreme cases when you have to go deep and fix stuff on low level (I have only like 2 such cases a year but each time it is really fun and a nice money 😉 ) When I’ll […]
Some time ago I wrote a simple tool to learn about Oracle data block internals – ODBV. The series of articles can be found here: https://blog.ora-600.pl/?s=odbv&submit= and the github repo is here: https://github.com/ora600pl/odbv This is not a production tool but during the last session in Birmingham at UKOUG_TECH17 – where I was doing a presentation […]
(Please tell me that I’m not the only one who thinks "Index Organized Table" instead of "Internet Of Things" when hearing IOT…) This post is inspired by Connor McDonald and his blog post from a year ago about direct mode operations and IOTs. You can read it here: https://connor-mcdonald.com/2016/07/04/direct-mode-operations-on-iots/amp/ While writing a redo parser for […]
While researching redo log internals for V00D00 we had to face the fact, that we know shit about real transactional behavior. When I say "real", I mean – under the hood. Even with a very simple stuff like COMMIT and ROLLBACK we were constantly amazed by the internal mechanisms. Today let’s take ROLLBACK under the […]
Before you proceed, please check out this short article written by Tanel Poder: https://blog.tanelpoder.com/2010/09/02/which-number-takes-more-space-in-an-oracle-row/ In the documentation, you can find the following explanation about the internal numeric format: Oracle stores numeric data in variable-length format. Each value is stored in scientific notation, with 1 byte used to store the exponent and up to 20 bytes […]
During a research for VOODOO, we came across a lot of interesting stuff inside REDO. One of my favourites is an UPDATE, becoming an INSERT 🙂 So let’s see what has happened – I performed the following update on a sample table: The regular dump of redo log with an UPDATE looks like this: In […]
Sorry for long time without post, but we are writing with Marcin Rydz a new heterogenous replication product based on archivelogs and it’s consuming a looooooot of our time 🙂 Yes I know it’s nothing new on the market. There are other cool products and I know they’ll be probably be better. But we want […]
Thanks to suggestions made by Frits Hoogland, I made some improvements to the ODBV. The new version can be found here: http://ora-600.pl/oinstall/odbv.x86_64 The changes are: Recognition of first, second and third level bitmap block Recognition of pagetable segment header Block number ranges on the left side The blocks will be coloured properly to belonging segment. […]
It’s time for the next article with ODBV visualisation 🙂 This time let’s examine the difference between move and shrink – this is very common question on a lot of trainings. You can find a lot of great articles in the Internet regarding this subject but I think that visualisation really helps to understand what […]