B-tree secondary-access method

Informix® provides the generic B-tree index for columns in database tables. In traditional relational database systems, the B-tree access method handles only built-in data types and therefore it can only compare two keys of built-in data types. The generic B-tree index is an extended version of a B-tree that Informix provides to support user-defined data types.

Tip: For more information about the structure of a B-tree index and how to estimate the size of a B-tree index, see Estimating index pages.
Informix uses the generic B-tree as the built-in secondary-access method. This built-in secondary-access method is registered in the sysams system catalog table with the name btree. When you use the CREATE INDEX statement (without the USING clause) to create an index, the database server creates a generic B-tree index. For more information, see the CREATE INDEX statement in the HCL Informix Guide to SQL: Syntax.
Tip: Informix also defines another secondary-access method, the R-tree index. For more information about how to use an R-tree index, see the HCL Informix R-Tree Index User's Guide.

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