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

DB2 V9 Dynamic Index ANDing
� Dynamic Index ANDing – Fact table access
–Filtering may not be (truly) known until runtime
RID
list 2
RID
list 2/3
RID
list 3
RID list
2/3/4
RID
list 4
Figure 4-3 Building the final RID list before E- fact table access
The final fact table RIDs are used to retrieve data from fact table and join back to
dimension table as necessary for obtaining data from dimension tables.
To summarize, the pair-wise join has the following characteristics:
1. Joins each dimension table with a fact table through an index independently
2. Performs RID Sort and RID Merge (ANDing) of the RID lists obtained from
step 1 to form the final fact table RID list
3. Fetches data from the fact table using the final RID list
4. Joins back the dimension table only if it has select out column from dimension
tables
4.2 Database statistics for BI tables
Remaining RID lists are
“ANDed” (intersected)
Final RID list used for parallel fact table
(and remaining dimension) access
© 2006 IBM Corporation
Processing RUNSTATS for BI tables and histogram statistics is a newly
introduced feature that can help you manage performance of your environment.
Chapter 4. Benefits of DB2 9 for SAP BI 39