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AdministeringIn addition to administering the database server, you can tune performance, replicate data, and archive data.
System administrationThese topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL OneDB™ database servers.
Performance GuideThe HCL OneDB™ Performance Guide describes how to configure and operate your HCL OneDB™ database server to improve overall system throughput and to improve the performance of SQL queries.
Fragmentation guidelinesOne of the most frequent causes of poor performance in relational database systems is contention for data that resides on a single I/O device. Proper fragmentation of high-use tables can significantly reduce I/O contention. These topics discuss the performance considerations that are involved when you use table fragmentation.
Distribution schemes that eliminate fragmentsFragment elimination is a database server feature that reduces the number of fragments involved in a database operation. This capability can improve performance significantly and reduce contention for the disks on which fragments reside.
Effectiveness of fragment eliminationThe database server cannot eliminate fragments when you fragment a table with a round-robin distribution scheme. Furthermore, not all expression-based distribution schemes give you the same fragment-elimination behavior.
Overlapping fragments on a single columnThe 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.

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.