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Observation: Low Index Cluster Ratio
The cluster ratio is less than the minimum accepted for clustering indexes. The DB2 optimizer attempts to use a clustering index before using other indexes defined for a table. Db2 will attempt to use an index with a high cluster ratio, that is, a cluster ratio greater than or equal to eighty percent, as follows:
To avoid sorts.
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When using LIKE predicates with host variables, if the host variable value begins with "%" or " ". DB2 can use a non-matching index scan instead of a tablespace scan
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If the Db2 optimizer determines that many data pages will be read, DB2 might invoke both leaf and data page prefetch to reduce the total cost of the read.
To improve the probability of the Db2 optimizer using the clustering index:
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Execute REORG to restore clustering.
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Run RUNSTATS to update statistics.
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Rebind affected plans.