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DB Performance: Set Query Comparison<br />
<br />
<br />
<br />
For both DB2 MVS & DB2 UDB, Query Plan for KN = K100K &<br />
K10K is: access rows with KN = 3 & test KSEQ in proper ranges<br />
DB2 MVS had .0001*(.06)*1,000,000 = 6 rows accessed for<br />
K10K; DB2 UDB with 10,000,000 rows, had 62 rows accessed<br />
In these cases of very low selectivity, index driven access to<br />
individual rows is still the best Query Plan<br />
KN Used<br />
In Q3B<br />
Rows Read<br />
(of 1M)<br />
DB2 MVS<br />
Index usage<br />
DB2 UDB<br />
Index usage<br />
DB2 MVS<br />
Time secs<br />
K100K 1 K100 K100 1.4 0.7<br />
K10K 6 K10K K10K 2.4 3.1<br />
DB2 UDB<br />
Time secs<br />
22
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