Category: Troubleshooting

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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...

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Understanding Return Codes in the DB2 Diagnostic Log

I learned a nifty little trick while troubleshooting a connection issue, and thought I would share. It can be useful in getting information out of the db2 diagnostic log. DB2 Diagnostic Log The DB2 diagnostic log has a wealth of information. After over 15 years working with DB2, I still learn new things about how to read it every single...

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Building a Sandbox VM for DB2

There are plenty of things that I want to try in a sandbox VM before I let them anywhere near even a development environment. Even if I didn’t use it constantly for blogging, I would still need it for trying things to see how they work before advising clients. These instructions should never be used to build a development, test,...

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Monitoring Extent Movement Progress

Since DB2 9.7, you have been able to reduce the size of tablespaces using the statement: ALTER TABLESPACE USERSPACE1 REDUCE MAX Using this functionality, however, requires that the tablespace uses automatic storage and that it was created with the reclaimable storage attribute. Unfortunately, tablespaces created in DB2 9.5 or earlier will not have the reclaimable storage attribute, and it’s not...