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The internal throughput rate for the two tests is shown in Figure 2-7. The ITR numbers show an improvement of 2.16% with the fast index traversal feature enabled. 

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The improved performance of the RTW workload with fast index traversal enabled is the result of a reduction in the number of getpage requests against the index buffer pools. In total, eight indexes were managed by using in-memory structures (FTBs) when INDEX_MEMORY_CONTROL was set to AUTO. The total average getpage requests per thread dropped from 289.4 K to 236.8 K (a 18.2% reduction) compared to INDEX_MEMORY_CONTROL set to DISABLE. 

Although the fast index traversal feature requires separate (extra) storage to store the in-memory managed indexes’ root and non-leaf pages, the test results by using the non-data sharing RTW workload show that setting INDEX_MEMORY_CONTROL to AUTO did not cause more Db2 real storage usage compared to when the workload was run with INDEX_MEMORY_CONTROL set to DISABLE. This result occurs because the RTW workload includes small indexes and all the FTBs only took up less than 1 MB of storage, as indicated by the -DISPLAY STATS(IMU)  command output. 

