Overlapping fragments on a single column

The fragments on a single column can be overlapping and noncontiguous. You can use any range, MOD function, or arbitrary rule that is based on a single column.

The only restriction for this category of fragmentation rule is that you base the fragmentation rule on a single column.

Example of overlapping fragments on a single column shows an example of this type of fragmentation rule.
Figure 1: Example of overlapping fragments on a single column
...
FRAGMENT BY EXPRESSION
a<=8 OR a IN (9,10,21,22,23) IN dbsp1,
a>10 IN dbsp2;

If you use this type of distribution scheme, the database server can eliminate fragments on an equality search but not a range search. This distribution scheme can still be useful because all INSERT and many UPDATE operations perform equality searches.

This alternative is acceptable if you cannot use an expression that creates nonoverlapping fragments with contiguous values. For example, in cases where a table is growing over time, you might want to use a MOD function rule to keep the fragments of similar size. Expression-based distribution schemes that use MOD function rules fall into this category because the values in each fragment are not contiguous.