In order to access a SAS
library, SAS needs a libref and a library engine name. For example,
you assign a libref to the SAS library with the LIBNAME statement
or the
New Library window, but usually you do not have to specify
an engine name because SAS automatically selects the appropriate engine.
If you do not specify
an engine, SAS automatically assigns one based on the contents of
the SAS library. For example, SAS is able to differentiate between
a SAS 6 library and a SAS 9 library. Note that in SAS 9, a SAS library
containing SAS 7 and SAS 8 files is the same as a SAS 9 library, because
the engine that creates a SAS file determines its format, and the
file format for SAS 7, SAS 8, and SAS 9 is the same.
For example, in a SAS
9 session, if you issue the following LIBNAME statement to assign
a libref to a SAS library containing SAS 8 files, SAS automatically
uses the SAS 9 engine:
libname mylib 'v8-SAS-library';
In a SAS 9 session,
if you issue the following LIBNAME statement to assign a libref to
a SAS library that contains only SAS 6 files, SAS automatically uses
the SAS 6 compatibility engine:
libname mylib 'v6-SAS-library';
SAS automatically assigns
an engine based on the contents of the SAS library as shown in the
following table:
Default Library Engine Assignment in SAS 9
|
|
|
|
|
No SAS files; the library
is empty
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Both SAS 9 SAS files
and SAS files from earlier releases
|
Note: Even though SAS automatically
assigns an engine based on the library contents, it is more efficient
for you to specify the engine. For example, specifying the engine
name in the following LIBNAME statement saves SAS from determining
which engine to use:
libname mylib v6 'v6-SAS-library';
For more
information about SAS engines, see SAS Engines.