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Best Practices for SAP BI using DB2 9 for z/OS - IBM Redbooks

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6.3.2 Benefits of remodeling InfoProviders<br />

Remodeling allows you to add, delete, or replace a characteristic or key figure to<br />

an InfoCube without having to reload the data. Remodeling is not as involved as<br />

in previous versions, thus providing you with improved flexibility.<br />

6.4 <strong>SAP</strong> compression <strong>for</strong> loads<br />

6.4.1 Advantages<br />

<strong>SAP</strong> compression is the consolidation and summarization of data from an<br />

iInfoCube’s F- fact table into its E- fact table. Compression in this manner differs<br />

from traditional <strong>DB2</strong> storage compression in that it does more than potentially<br />

reduce data storage requirements.<br />

Implementing <strong>SAP</strong> compression from the F- fact table to the E- fact table, in<br />

conjunction with <strong>SAP</strong> partitioning of the E- fact table, is one of the most important<br />

factors in having good load and query per<strong>for</strong>mance.<br />

A request is always loaded into the F- fact table. Compression copies the data<br />

into the E- fact table. Records in different requests that characteristics are all the<br />

same are merged into one record of the E- fact table. For non-cumulative cubes,<br />

an additional request containing the actual values of key figures is updated.<br />

These records are called reference points. At the end, the request is deleted<br />

from the F- fact table.<br />

There are several advantages to <strong>using</strong> <strong>SAP</strong> compression <strong>for</strong> loading data into E-<br />

fact tables. Some of those advantages are:<br />

► <strong>SAP</strong> compression reduces the number of rows in the F- fact table (sometimes<br />

to zero).<br />

– A smaller F- fact table results in accelerated loading into the F- fact table.<br />

– <strong>SAP</strong> compression permits faster updating of the F- fact table indexes.<br />

– It accelerates aggregate rollups, since the F- fact table is the source of<br />

data <strong>for</strong> rollup.<br />

– It shortens RUNSTATS processing time on the F- fact table.<br />

– It reduces index REBUILD processing time if indexes are dropped as part<br />

of load.<br />

96 <strong>Best</strong> <strong>Practices</strong> <strong>for</strong> <strong>SAP</strong> <strong>BI</strong> <strong>using</strong> <strong>DB2</strong> 9 <strong>for</strong> z/<strong>OS</strong>

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