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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.
Improving individual query performanceYou can test, monitor, and improve queries.
Improve filter selectivityYou can control the amount of information that a query evaluates. The greater the precision with which you specify the desired rows, the greater the likelihood that your queries will complete quickly.
Avoid some filtersFor best performance, avoid filters for certain difficult regular expressions and filters for noninitial strings.
Avoid noninitial substringsFor best performance, avoid filters for noninitial strings. A filter based on a noninitial substring of a column requires the database server to test every value in the column.

Avoid noninitial substrings

For best performance, avoid filters for noninitial strings. A filter based on a noninitial substring of a column requires the database server to test every value in the column.

For example, in the following code, a noninitial substring requires the database server to test every value in the column:

SELECT * FROM customer 
   WHERE zipcode[4,5] > '50'

The database server cannot use an index to evaluate such a filter.

The optimizer uses an index to process a filter that tests an initial substring of an indexed column. However, the presence of the substring test can interfere with the use of a composite index to test both the substring column and another column.