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

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– Improved bufferpool hit ratio (more rows per page)<br />

– Reduced log data volume where there is insert-intensive processing<br />

With the compression dictionary moving above the 2 GB bar in V8, which may<br />

result in virtual storage relief <strong>for</strong> DBM1, there is more motivation <strong>for</strong><br />

customers to exploit System z strong compression capabilities.<br />

10.Use the <strong>SAP</strong> transaction/programs to remove unused data.<br />

Master data tables can be preloaded with <strong>SAP</strong> default data and loaded with<br />

data by a user that never gets utilized. This unused data can disrupt the<br />

cost-based optimizer's estimates of how many rows will be returned, or can<br />

result in this data being unnecessarily retrieved <strong>for</strong> every query involving that<br />

table.<br />

We recommend purging unwanted data <strong>using</strong> the following methods:<br />

– Trancode RSRV <strong>for</strong> dimension data.<br />

– The program to delete master data is RSDMD_DEL_BACKGROUND or<br />

functional module RSDMD_DEL_MASTER_DATA.<br />

– The program RSCDS_DEL_OLD_REQUESTS removes obsolete rows<br />

from F- fact tables (<strong>SAP</strong> note 609164).<br />

Chapter 3. Top ten <strong>SAP</strong> <strong>BI</strong> recommendations 33

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