The MySQL Cluster data node log files can become very big. The best solution is to actually fix the underlying problem. But if you know what you are doing, you can work around it and filter out these annoying log entries.

An example of ‘annoying’ entries is when you run MySQL Cluster on virtual machines (not good!) and disks and OS can’t follow any more; a few lines from the ndb_X_out.log:

2011-04-03 10:52:31 [ndbd] WARNING  -- Ndb kernel thread 0 is stuck in: Scanning Timers elapsed=100
2011-04-03 10:52:31 [ndbd] INFO     -- timerHandlingLab now: 1301820751642 sent: 1301820751395 diff: 247
2011-04-03 10:52:31 [ndbd] INFO     -- Watchdog: User time: 296  System time: 536
2011-04-03 10:52:31 [ndbd] INFO     -- Watchdog: User time: 296  System time: 536
2011-04-03 10:52:31 [ndbd] WARNING  -- Watchdog: …

Isolation is an important part of ACID properties that guarantee that transactions are processed in a reliable manner. But there are four different levels of isolation available and you have to understand each one of them to be able to select the correct one for your needs. This post intends on explaining the four levels together with their effects on locking and performance.

I always remember the saying that tomorrow is the first day of the rest of your life.  It refers to taking each day as it comes and making the best of it, and not concerning yourself with what you can no longer change - the past. This has new resonance for me today as tomorrow I start on a new job, as Webmaster for SkySQL Ab.

For the last five and a half years I've worked for MySQL in all its forms.  Initially MySQL AB, then the Database Group in Sun Microsystems, and finally the Open Source business unit in Oracle. (For anyone still at Oracle, forgive me if I get the names wrong, I don't think I ever fully worked out what our group's official name was).  For most of that time I've loved every minute of it, working with great people on a great product and bringing it to the world (or at least the World Wide Web in my case).

Now I get to work with some great people, …

The O'Reilly MySQL 2011 conference is coming up fast.  It should be a good conference as it covers the increasingly diverse MySQL community and MySQL alternatives very well.   As usual, there are some painful choices about which talks to attend.  I'm doing two talks myself that I hope you have on your list:

• Curing Replication Deprivation with Tungsten -- A tutorial together with my colleague Ed Archibald.  It covers everything you ever wanted to know about how to use parallel replication, handle multi-master/multi-source, replication to PostgreSQL/Oracle, etc.  We will have a short section at the end about how to build full clusters with Tungsten Enterprise.   Giuseppe Maxia is threatening to join and do some of his famous …

Unlike most other MySQL storage engines, Ndb does not perform all of its work in the MySQLD process. The Ndb table handler maps Storage Engine Api calls onto NdbApi calls, which eventually result in communication with data nodes. In terms of layers, we have SQL -> Handler Api -> NdbApi -> Communication. At each of these layer boundaries, the mapping between operations at the upper layer to operations at the lower layer is non trivial, based on runtime state, statistics, optimisations etc.

The MySQL status variables can be used to understand the behaviour of the MySQL Server in terms of user commands processed, and also how these map to some of the Storage Engine Handler Api calls.

Status variables tracking user commands start with …

Spring is making its way into everything, and the databases are blooming as the DBAs who manage them are savoring the fragrance of the changing weather and fresh new ideas in the world of blogging. In order to appreciate the springing blogging innovations, this week’s Log Buffer, Log Buffer #215 picks some of the flowers just for you.

Oracle:

Hemant, the Oracle ACE from Singapore writes superbly about OuterJoin with Filter Predicate as usual with a reproducible case.

When …

Sometimes the question is put like are you looking for Performance OR Stability, which I believe is a strange way to put it. In real life systems you care both about Performance AND Stability. I would even say Stability is a not the best world here, I would day you care about your minimal performance in most cases.

If system can handle 5000 q/sec for 1 minute and when 20.000 s/sec for the next one, how much I can count on in terms of capacity planning ? In case this is typical OLTP system I will have to use 5000 q/sec number as I need my system to always be able to reach performance requirements. If the system though is doing batch processing may be I can count on the average which is 12.5K in this case.

The difference between stability and minimal performance is important as I can be quite OK with “unstable” performance if it is performance bursts rather than stalls, for example if my system performs 7000 q/sec and …

FromDual has released today the next version v0.6 of its FromDual Performance Monitor for MySQL.

The most important improvement of the new release is the new monitoring module for DRBD devices which are often used in MySQL High Availability (HA) set-ups.

More information about the new functionality added you can find in the article MySQL Performance Monitor with DRBD monitoring capabilities, MySQL Performance Monitor and in the MySQL HA (high availability) cookbook.

The FromDual Performance Monitor for MySQL is now available on our download page.

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Monty just got interviewed by Packt Publishing in a Q&A format. There’s no way to comment on that article, so I’m wondering if you have any feedback — drop it here.

Also decided to start collecting interviews related to MariaDB on the Knowledgebase. Remember that its open for all to edit, so sign up.

I tried to come up with a number of topics for this post, but none seemed to really convey what I really feel.. And really this blog is about all of them..

• A look at PERFORMANCE_SCHEMA.STAGES and PERFORMANCE_SCHEMA.STATEMENTS
• Graphing MySQL Statement Execution
• A MySQL visual EXPLAIN plan with PERFORMANCE_SCHEMA
• Tracing Sessions with PERFORMANCE_SCHEMA

If that doesn’t whet your appetite (and trust me, I need to, this post is long, but I feel is worth reading all the way to the end), then let me start out by asking the question:

Wouldn’t you like to be able to trace what a SQL statement did, either in the same or another session, on a production instance, after the fact? Wouldn’t you like to know where all of it’s time was spent, and some statistics on what it was doing specifically?

I know, …