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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.
Strategy for fragmenting indexesWhen you fragment a table, the indexes that are associated with that table are fragmented implicitly, according to the distribution scheme that you use, except for the round-robin fragmentation scheme when automatic location is enabled. Indexes on tables that use the round-robin distribution scheme are not fragmented when the AUTOLOCATE configuration parameter or environment option is set to a positive integer. You can use the FRAGMENT BY clause of the CREATE INDEX statement to fragment the index on any table.When you fragment a table, the indexes that are associated with that table are fragmented implicitly, according to the distribution scheme that you use. You can use the FRAGMENT BY clause of the CREATE INDEX statement to fragment the index on any table.
Restrictions on indexes for fragmented tablesIf the database server scans a fragmented index, multiple index fragments must be scanned and the results merged together. (The exception is if the index is fragmented according to some index-key range rule, and the scan does not cross a fragment boundary.) Because of this requirement, performance on index scans might suffer if the index is fragmented.

Restrictions on indexes for fragmented tables

If the database server scans a fragmented index, multiple index fragments must be scanned and the results merged together. (The exception is if the index is fragmented according to some index-key range rule, and the scan does not cross a fragment boundary.) Because of this requirement, performance on index scans might suffer if the index is fragmented.

Because of these performance considerations, the database server places the following restrictions on indexes:

You cannot fragment indexes by round-robin.
You cannot fragment unique indexes by an expression that contains columns that are not in the index key.

For example, the following statement is not valid:

CREATE UNIQUE INDEX ia on tab1(col1)
   FRAGMENT BY EXPRESSION
      col2<10 in dbsp1,
      col2>=10 AND col2<100 in dbsp2,
      col2>100 in dbsp3;