MQT does not need to be current to the second, changes can be captured in 

a staging table and applied on any schedule. 

10.7  Multidimensional clustering (MDC)

This section gives a brief introduction about the 

Multidimensional Clustering 

(MDC)

 feature provided by DB2 UDB, Version 8.1.

DB2 UDB in earlier versions provides the feature for single dimensional data 

clustering. This was maintained by physically clustering the data on insert, 

according to the order of one single clustering index. The number of clustering 

indexes per table is limited to one.

Figure 10 3 shows data clustering according to one single index, in this case the 

Region

 index. 

Clustering

Index

on Region

Table

Index

on Year

Figure 10 3   One clustering index

One of the main drawbacks of this clustering method is that clustering degrades 

over time and requires the use of the 

REORG 

utility from time to time to put the 

index back in order.

Another drawback of this method is that the indexes are record based, and is 

what makes them often very large.

 Chapter 10. Advanced DB2 UDB features 

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