189 Search results

For the term "index".
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Multiple Index Regression Analysis

I actually had a blog entry started on this topic before IDUG. I knew this was possible, but not exactly how to do it. Then I sat in Scott Hayes’ session – D04 – More Sage Advice: Invaluable DB2 LUW Performance Insights from Around the Globe, and he had all the details I needed to really get rolling on trying...

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Clustering a Table on an Index

I have been playing a fair amount lately with clustering indexes and have been rehashing my views on reorging tables on an index. This is still a work in progress, but thought I’d share some details and see if others out there have any thoughts to share with me and others on it. Clustering a Table on an Index I’ve...

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Example of A Clustering Low-Cardinality Index Helping Query Performance

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. In this case, this query is related to the...

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When Index Scans Attack!

We all know that table scans can be (but aren’t always) a negative thing. I have spent less time worrying about index scans, though. Index access = good, right? I thought I’d share a recent scenario where an index scan was very expensive. Maybe still better than a table scan, but with one index, I reduced the impact of a...

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How to Tell When an Index Reorg is Needed

My earlier post on table reorgs covered Reorg’s place in a database maintenance cycle and running reorgchk. If you haven’t already read it, check it out: How to Tell When a Table Reorg is Needed INDEXES After the section on tables, REORGCHK output has a section with details on each index for each table that REORGCHK looked at. The index...