When you create an index of type CTXCAT, you must use the CATSEARCH operator to enter your query. An index of type CTXCAT is best suited when your application stores short text fragments in the text column and other associated information in related columns.
For example, an application serving an online auction site might have a table that stores item description in a text column and associated information such as date and price in other columns. With a CTXCAT index, you can create b-tree indexes on one or more of these columns. The result is that when you use the CATSEARCH operator to search a CTXCAT index, query performance is generally faster for mixed queries.
The operators available for CATSEARCH queries are limited to logical operations such as AND or OR. The operators you can use to define your structured criteria are greater than, less than, equality, BETWEEN, and IN.