SAS 9.4 Language Reference, 6th Edition

SAS libraries can contain files that you create, or they can be one of several special

libraries that SAS provides for convenience, support, and customizing capability such as

the Work library. SAS does not limit the number of SAS files that you can store in a SAS

library.

Library Engines

Each SAS library is associated with a library engine. SAS library engines are software

components that form the interface between SAS and the SAS library. It is the SAS

library engine that locates files in a SAS 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 Multi 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 SAS 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 might be involved in processing a DATA step; for example, one

engine might be used to input data, and another engine might be used to write

observations to the output data set.

For more information about library engines, including a list of engines available in Base

SAS, see “About Library Engines” on page 750.

Library Names

Physical Names and Logical Names (Librefs)

Before you can use a SAS library, you must tell SAS where it is. SAS recognizes SAS

libraries based on either operating environment naming conventions or SAS naming

conventions. There are two ways to define SAS libraries:

• a physical location name that the operating environment recognizes

• a logical name (libref) that you assign using the LIBNAME statement, LIBNAME

function, or the New Library window

Library Names 587