Library Engines

Each SAS data library is associated with a library engine. SAS library engines are software components that form the interface between SAS and the SAS data library. It is the SAS library engine that locates files in a SAS data library and renders the file contents to SAS in a form that it can recognize. Library engines perform such tasks as:

• reading and writing data

• listing the files in the library

• deleting and renaming files.

SAS has a Multiple Engine Architecture in order to read to and write from files in different formats. Each SAS engine has specific processing characteristics, such as the ability to

• process a SAS file generated by an older version of SAS

• read database files created by other software programs

• store and access files on disk or tape

• determine how variables and observations are placed in a file

• place data into memory from its physical location

• transport SAS files between operating environments.

You generally are not aware of the particular type of engine that is processing data at any given time. If you issue an instruction that is not supported by the engine, an error message is displayed in the log. When needed, you can select a specific engine to perform a task. But usually, you do not have to specify an engine, because SAS automatically selects the appropriate one.

More than one engine may be involved in processing a DATA step; for example, one engine may be used to input data, and another engine may be used to write observations to the output data set.

For more information on library engines, including a list of engines available in Base SAS, see 'About Library Engines' on page 602.