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

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

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Figure 4-2 and Figure 4-3 on page 39 show the principle of processing dynamic<br />

index ANDing <strong>for</strong> pre- fact table access. Unlike traditional star join group, the<br />

pair-wise join represents each dimension table join with fact table separately.<br />

The result of each pair-wise join is a set of RIDs of F- fact table. The RIDs are<br />

ANDing together produce a final RID list <strong>for</strong> accessing the E- fact table pages.<br />

<strong>DB2</strong> V9 Dynamic Index ANDing<br />

� Dynamic Index ANDing – Pre-fact table access<br />

DP<br />

F<br />

RID<br />

list 1<br />

Figure 4-2 Pre- fact table access<br />

38 <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><br />

–Filtering may not be (truly) known until runtime<br />

DT<br />

F<br />

RID<br />

list 2<br />

X2 S2<br />

D2<br />

F<br />

RID<br />

list 3<br />

X1 S1<br />

D4<br />

F<br />

RID<br />

list 4<br />

Filtering dimensions are<br />

accessed in parallel<br />

Join to respective fact<br />

table indexes<br />

Build RID lists<br />

� Runtime optimizer may terminate parallel<br />

leg(s) which provide poor filtering at runtime<br />

© 2006 <strong>IBM</strong> Corporation

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