An extspace is a logical name associated with an arbitrary string that signifies the location of external data. The resource that the extspace references depends on a user-defined access method for accessing its contents.

For example, a database user might require access to binary files encoded in a proprietary format. First, a developer creates an access method, which is a set of routines that access the data. These routines are responsible for all interaction between the database server and the external file. A DBA then adds an extspace that has the file as its target to the database. After the DBA creates a table in the extspace, the users can access the data in the proprietary files through SQL statements. To locate those files, use the extspace information.

An extspace is not required to be a file name. For example, it can be a network location. The routines that access the data can use information found in the string associated with the extspace in any manner.

For more information about user-defined access methods, see the IBM® Informix® Virtual-Table Interface Programmer's Guide. For more information about creating functions and primary access methods, see the HCL Informix Guide to SQL: Syntax.

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