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

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Figure 7-1 shows the initial status of the indexes on a new DataStore object.<br />

Figure 7-1 Initial status of indexes on DataStore object<br />

The creating of a secondary index should be analyzed carefully.<br />

Indexes, by nature, consume resources such as storage, memory, and CPU<br />

cycles to be maintained. Conversely, when the index is correctly selected, it<br />

improves per<strong>for</strong>mance. The DataStore objects are normally written on large data<br />

loads when having an index is an additional load. In this case we recommend<br />

that the index be deleted be<strong>for</strong>e the data load and then recreated <strong>for</strong> improved<br />

query per<strong>for</strong>mance. This procedure has to be analyzed, taking into consideration<br />

the time that the data load is penalized <strong>for</strong> the index maintenance compared to<br />

the time <strong>for</strong> deletion and recreation of the index.<br />

106 <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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