Db2 Experts on a Data Science Quest
This is a new series that has been percolating in my head for a while. When I help clients with SQL, we’re often adding (or removing) indexes to help SQL performance. It has been said (though not by me) that SQL re-write is obsolete because the Db2 Optimizer will take care of that.… Read the rest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
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Explain tables change in structure from version to version of DB2. If you want to continue to use the same set of explain tables across a DB2 upgrade, you must take special action to upgrade them.
Explain tables are used when generating a human-readable version of the access plan for a query.… Read the rest
Continue reading »While this post is specific to WebSphere Commerce, it covers concepts that may apply to tuning other delete statements as well.
The CLEANCONF table stores the delete statements that are used by DBCLEAN. Most of them use syntax like this for the date component:
(days(CURRENT TIMESTAMP) - days(prevlastsession)) = ?… Read the rest Continue reading »
GENERATED ALWAYS can be a blessing or a curse. I’m not talking about identity columns here, but about creating a column that is actually a duplicate of some part of the data to boost performance. Sure, in 10.5 we can do indexes on expressions, but for some clients I have trouble just getting them to go to a supported level, much less the latest and greatest.… Read the rest
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Have you ever looked at a list of tables in your database, only to see the set of EXPLAIN tables present in two, five or even 10 different developers’ schemas?
I don’t know about you, but this drives me crazy.… Read the rest
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I had been in conversation with a respected DBA who is a well known speaker and author. I had mentioned how difficult it is to come up with advanced topics to write and speak about. That is when he responded “Advanced topics only narrow the audience”.… Read the rest
Continue reading »To go with my recent article on RCAC/FGAC, I thought I would do some similar work using LBAC and see what I could learn about it and the differences between the two.
Label Based Access Control essentially adds a column to a table that labels each row (think confidential, secret, top secret), and then grants uses of those labels to users to allow them to access the data.… Read the rest
Continue reading »DB2 10.1 introduced a new feature commonly called RCAC (Row and Column Access Control) or FGAC(Fine-Grained Access Control). This is a bit less labor intensive to support than LBAC (Label Based Access Control), and solves some of the problems with LBAC.… Read the rest
Continue reading »I’m always keeping an eye on Twitter to catch interesting bits of news, and that includes watching cross platform information. I find it fascinating to compare DB2 to other RDMBSes, and saw a great article from Use the Index, Luke (fabulous name!)… Read the rest
Continue reading »The request from the developers was something along the lines of “Help, Ember, this query needs to perform better”. Sometimes the query I’m working on is not one that shows up as a problem from the database administrator’s perspective, but one that is especially important in some part of application functioning.… Read the rest
Continue reading »There are a lot of things I can cover on db2top, and probably more tips and tricks using db2top than many other tools out there. Searching the web on db2top gets more good results than on many other db2 topics. I thought I’d start with some of the basics.… Read the rest
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