Improved query performance through fragmentation strategy

If the primary goal of fragmentation is improved performance for individual queries, try to distribute all of the rows of the table evenly over the different disks. Overall query-completion time is reduced when the database server does not need to wait for data retrieval from a table fragment that has more rows than other fragments.

If queries access data by performing sequential scans against significant portions of tables, fragment the table rows only. Do not fragment the index. If an index is fragmented and a query has to cross a fragment boundary to access the data, the performance of the query can be worse than if you do not fragment.

If queries access data by performing an index read, you can improve performance by using the same distribution scheme for the index and the table.

If you use round-robin fragmentation, do not fragment your index. Consider placing that index in a separate dbspace from other table fragments.

For more information about improving performance for queries, see Query expressions for fragment elimination and Improving individual query performance.

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