A hub for sharing relational database knowledge and experimentation
Database performance is heavily influenced by data volume and cardinality (or how unique that data may be).
It’s interesting to watch the look on someone’s face when this concept clicks. There is a look of understanding from a developer when she can extrapolate why SQL ran in seconds on a small, local, dockerized, database but the same SQL runs in minutes in a much larger QA environment.… Read the rest
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“Relational databases don’t scale!”. This is the claim that database experts have heard over and over again, and yet we spend our careers scaling databases. I immediately translate this in my head to either “I threw hardware at the problem and it didn’t work!”… Read the rest
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Edited 12/13/2017 to correct image and details about the database heap.
Db2 memory management is a complex topic that I’ve already written about from several perspectives, and have a few blog entries in mind to explore further. A presentation that Melanie Stopfer gave a while back really helped me understand STMM better.… Read the rest
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I often lean on analogies when I speak to non-technical people about technical topics. For example, I would explain database locking as “two kids fighting for the same candy bar”. If you introduce isolation levels into the conversation, I would expand the analogy to include “one sibling holding on to a candy bar they care nothing about just because they don’t want the other sibling getting to it”.… Read the rest
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While I have tuned backup performance before, it has often been through physical database changes (spreading tables across more table spaces) that I achieve my greatest results. This post is not about backup performance tuning, but about solving a specific backup duration mystery.… Read the rest
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Some of the more complicated work a DBA does is often analyzing a query. Whether it is proactive or in response to a performance problem, there are so many factors that go into query performance. Even when looking at a query that has a performance problem, there is only occasionally a single, obvious cause for all of the problems.… Read the rest
Continue reading »I think that one of my least favorite phrases is “Nothing else changed!” More common than a performance problem that simply slowly creeps up with performance getting worse and worse over time is the sudden performance problem. Many times, sudden database performance problems can be mapped back to a specific change at some level.… Read the rest
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I have some very specific perspectives on monitoring DB2. In addition to regular consulting in my day job, we also provide full-service virtual DBA services, including monitoring. The monitoring we choose to do is very much under my control, and I’m constantly working on enhancements.… Read the rest
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dsmtop is a long-awaited refresh of the wildly popular db2top. Like db2top, dsmtop is a free tool, included with DB2. It is in the base DB2 install starting with 11.1, and can be installed on DB2 10.1 or 10.5.
As I personally recall, db2top first came out of IBM AlphaWorks.… Read the rest
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I am consistently shocked and appalled at how few clients actually do load testing. Many pay it lip service, but few actually engage in real, meaningful performance and load testing. I understand that load testing of an application can be difficult and expensive.… Read the rest
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A number of new clients I’ve worked with lately have had minor or major runstats or reorg issues. I have tons of advice on runstats and reorgs across many blog entries, but I don’t have one place where all that advice is brought together.… Read the rest
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The package cache is just one memory area that DB2 offers to tune memory usage for a DB2 database. This article is a deep dive into this memory area.
The package cache is an area of memory that DB2 uses to store access plans.… Read the rest
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