Category: Troubleshooting

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Query Performance Analysis

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. Defining...

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Comparing Two Db2 Systems

Sometimes configuration needs to be kept in sync between two or more Db2 systems. There are a variety of reasons – sometimes this is for keeping two HADR servers in sync, and other times it may be for keeping a dev, QA, or Staging system in sync with production. In any case, having an idea of what needs to be...

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Nothing Changed! A DB2 LUW Performance Investigation

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. Nothing Changed! Other times, everyone involved...

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Troubleshooting with Mickey Mouse, Snow White, and Cinderella

It’s that magical time of year again. DBAs excitedly pack their bags for a week-long trip. On-call rotation is hurriedly passed to the next poor soul on the rotation list. Ember dons her trademark pigtails. Melanie Stopfer crams another 20 slides into and already packed presentation. It’s time for the IDUG North American Technical Conference in Anaheim, California. All your...

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Determining Log Span

Some time ago, I wrote a post that suggested using the NUM_LOG_SPAN database configuration parameter to prevent long-running transactions from filling your transaction log. Using NUM_LOG_SPAN will indeed prevent the problem of long running transcations causing log file saturation, but what if you just want to find applications could become a problem, before the problem happens? Understanding LSNs Most DBAs...

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Comparing dsmtop and db2top

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. History of db2top As I personally recall, db2top first came out of IBM AlphaWorks. My understanding of IBM AlphaWorks is that...

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Finding the Subnet Mask on AIX

This is something DB2 DBAs may need to do as a part of setting up TSAMP. Nearly every server I’ve done before has had a subnet mask of 255.255.255.0, but I ran into a server recently that wasn’t, and thought I would share how I figured out what it should be (alone, in the middle of the night, during an...

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IBM’s DB2 RFE Program

RFE stands for “Request for Enhancement”. IBM has this program for a number of products, but until late 2016, the RFEs for DB2 on LUW were not publicly available to vote on. Now they are, and we’re seeing action on them. The Problem It can be frustrating to have an issue that IBM describes as “working as designed”. Sometimes these...

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The Role of the DB2 DBA in Load/Performance Testing

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. It is not something that every developer has as a part of their toolkit. But the most...