Designing and Maintaining Indexes
There are some differences between index support in the Embedded Database and databases accessed using the DataFlex SQL Drivers. If you are using SQL tables, read SQL Indexes.
Each embedded database table may have up to 15 indexes, each with up to 16 segments (columns) in them, and each having an aggregate key length of up to 256 bytes. Indexes are created and modified in the Table Editor. They can be re-sorted interactively through the Database Builder tool, and can also be updated from running programs by use of the sort command.
As explained in Finding Records, indexes are vital not only for finding records that users explicitly seek, but also for finding (sometimes internally, without display) records in related tables. Indexes are essential to the implementation of table relationships. The distinction between unique and non-unique indexes is also discussed there, as is the meaning of "Main index" with regard to a column.