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DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

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The reduction in CPU of DPSI is due to better code method: Load instead of INSERT as in<br />

the NPI case. Note that in the DPSI test case the BUILD2 phase is eliminated.<br />

In Figure 5-24 we compare the reorganization of a single partition of a 20 M rows table with<br />

10 partitions with 5 NPIs or 5 DPSIs versus the reorganization of the whole table.<br />

Reorg tablespace of 20M rows, 10 partitions with 5 DPSI or<br />

5 NPI<br />

time<br />

in<br />

seconds<br />

700<br />

600<br />

500<br />

400<br />

300<br />

200<br />

100<br />

0<br />

5 DPSI<br />

single part<br />

Figure 5-24 REORG with 5 NPIs vs. 5 DPSIs<br />

5 NPI<br />

single part<br />

5 DPSI<br />

whole table<br />

5 NPI<br />

whole table<br />

CPU 66 208 658 650<br />

Elapsed time 41 78 354 338<br />

The single partition reorganization compared to the previous reorganization test case with 1<br />

NPI or 1 DPSI shows a bigger reduction in CPU <strong>for</strong> 5 DPSIs compared to 5 NPIs because the<br />

index keys were loaded <strong>for</strong> all DPSI index physical partitions while keys were inserted to all 5<br />

NPI index logical partitions during the BUILD2 phase. Contention on NPIs is possible.<br />

In case the whole table is reorganized, the DPSI case shows a slight increase in CPU<br />

compared to the NPI case. In this case 5 NPI data sets vs. 50 DPSI data sets are loaded in<br />

the index Build phase.<br />

In Figure 5-25 we compare the rebuilding of a partition of a PI, NPI and DPSI.<br />

Chapter 5. Availability and capacity enhancements 251

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