How SAS Data Sets Are Accessed
shows how SAS data sets are accessed through an engine.
How SAS Data Sets Are Accessed
- Your data is stored in files for which SAS provides an engine.
When you specify a SAS data set name, the engine locates the appropriate
file or files.
- The engine opens the file and obtains the descriptive information
that is required by SAS, for example, which variables are available and what
attributes they have, whether the file has special processing characteristics
such as indexes or compressed observations, and whether other engines are
required for processing. The engine uses this information to organize the
data in the standard logical form for SAS processing.
- This standard form is called the SAS data file, which
consists of the descriptor information and the data values organized into
columns (referred to as "variables") and rows (referred to as "observations").
- SAS procedures and DATA step statements access and
process the
data only in its logical form. During processing, the engine executes whatever
instructions are necessary to open and close physical files and to read and
write data in appropriate formats.
Just as data that is accessed by an engine is organized into the SAS
data set model, groups of files that are accessed by an engine are organized
in the correct logical form for SAS processing. Once files are accessed as
a SAS data library, you can use SAS utility windows and procedures to list
their contents and to manage them. See SAS Data Libraries for more information about SAS data libraries.
Relationship of Engines to SAS Data Libraries shows
the relationship of engines to SAS data libraries.
Relationship of Engines to SAS Data Libraries
Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.