Chapter 4: Using SAS Files


Introduction to SAS Files

What Is a SAS File?

SAS creates and uses a variety of specially structured files called SAS files . Although Windows manages the file for SAS by storing it, the operating system cannot process it. For example, you can list SAS files with the Windows Explorer, but SAS files can only be processed by SAS. SAS files are different from external files. While external files can be processed by SAS statements and commands, they are not managed by SAS.

SAS files usually reside in SAS data libraries. Under Windows, a SAS library is simply a named collection of SAS files within one or more Windows folders that SAS can access . Each SAS data library has an access engine associated with it the first time that a file in the library is accessed. The engine name specifies the access method that SAS uses to process the files in the data library. SAS data libraries are described in detail in SAS Language Reference: Concepts .

The various engines enable SAS to access different formats or versions of SAS files and other vendors files. For this reason, SAS is said to have Multiple Engine Architecture. Multiple Engine Architecture, combined with conversion utilities, provides access to SAS 9.1 files and SAS files created with previous releases of SAS (back to Version 5), whether they were created under Windows or other operating environments. Multiple Engine Architecture also provides access to files created by other vendors products, including database files.

The following sections highlight information you need in order to create and use SAS files with the various engines under Windows.

File Extensions for SAS Files

SAS files are stored in SAS data libraries and are referred to as members of a library. Each member has a member type . SAS distinguishes between SAS files and external Windows files in a folder by using unique file extensions. SAS assigns certain file extensions to a general set of SAS member types. The following table lists the Windows file extensions and their corresponding SAS member types for the V6, V7, V8, and V9 engines. For more information about engines, see Multiple Engine Architecture on page 122.

Table 4.1: Windows File Extensions and Their Corresponding SAS Member Types

V6 File Extension

V7 and Beyond File Extensions

SAS Member Type

Description

.sas

.sas

none

SAS program

.ss2

.sas7bpgm

Program

stored program (DATA step)

 

.cfg (Version 8 and beyond)

none

configuration file

.lst

.lst

none

output file

.log

.log

none

log file

none

.sas7baud

Audit

audit file

.sd2

.sas7bdat

Data

data set

.sv2

.sas7bvew

View

data set view

.si2

.sas7bndx

Index

data set index. Indexes are stored as separate files but are treated by SAS as integral parts of the SAS data file.

.sc2

.sas7bcat

Catalog

SAS catalog

.sa2

.sas7bacs

Access

access descriptor file

.sf2

.sas7bfdb

FDB

consolidation database file

.sm2

.sas7bmdb

MDDB

multi-dimensional database file

none

.sas7bdmd

DMDB

data mining database file

none

.sas7bitm

Itemstor

item store file

.su2

.sas7butl

Utility

utility file

.sp2

.sas7bput

Utility

permanent utility

.stx

none

none

transport file

none

.sas7bbak

none

backup file

CAUTION:

  • Do not change the file extension of a SAS file; doing so can cause unpredictable results. The file extensions assigned by SAS to SAS files are an integral part of how SAS accesses these files. Also, you should not change the filename of a SAS file using operating system commands. If you want to change the name of a SAS file, use the DATASETS procedure or select the file in the SAS Explorer window or the My Favorite Folders window and select

    Edit Rename

Note: Be sure not to delete files from your Work and Sasuser data libraries during your SAS session. SAS creates temporary utility files that you do not need to access directly but that are necessary for processing SAS data.

If your SAS session ends abnormally, you might need to delete files outside SAS in order to regain disk space. You can delete files in the Work library by using the WORKINIT and the WORKTERM system options when you start SAS. For more information, see WORKINIT System Option and WORKTERM System Option in SAS Language Reference: Dictionary .

SAS Data Sets (Member Type: Data or View)

SAS data set is an umbrella term for SAS data files and SAS data views, which are both discussed here. This section provides a brief overview of the concept of SAS data sets. For complete details, see the data sets section in SAS Language Reference: Concepts .

Logically, a SAS data set consists of two types of information: descriptor information and data values. The descriptor information includes such things as data set name, data set type, data set label, and number of variables , as well as the names and labels of the variables in the data set, their types (character or numeric), their length, their position within a record, and their formats. For more information, see CONTENTS Procedure on page 425.

The data values contain values for the variables. A SAS data set can be visualized as a table consisting of rows of observations and columns of variable values. The following table illustrates the SAS data set model.

click to expand
Figure 4.1: SAS Data Set Model

SAS data files (member type: Data)

  • The SAS data file is probably the most frequently used type of SAS file. SAS data files have a SAS member type of Data and are created in the DATA step and by certain SAS procedures such as the RANK procedure in Base SAS software. SAS data files have a file extension of .sas7bdat.

    SAS defines two types of SAS data files, native and interface. Native data files store data values and descriptor information, as described earlier, in files formatted by SAS. These are the SAS data sets you may be familiar with from previous versions of SAS under other operating environments. In SAS under Windows, native SAS data files can be indexed. The index is an auxiliary file that you create to provide fast access to records within a SAS data file through a variable or key. Indexes are stored as separate files but are treated by SAS as integral parts of the SAS data file. To learn more about indexes, see SAS Language Reference: Concepts .

    The second type of data file is the interface SAS data file. These files store data in a file formatted by other software. Examples of interface SAS data files are BMDP, OSIRIS and SPSS files, which SAS can access as read-only files. For more information, see Reading BMDP, OSIRIS and SPSS Files on page 140.

SAS data views (member type: View)

  • SAS data views have a member type of View. They describe data values and tell SAS where to find the values, but they do not contain the actual data values themselves . SAS data views have a file extension of .sas7bvew.

    Views may be of two kinds, native or interface. A native SAS data view is created with the SQL procedure or with the DATA step and describes a subset or combination of the data in one or more SAS data files or SAS data views. For information on SQL views, see the Base SAS Procedures Guide . For information on DATA step views, see SAS Language Reference: Concepts .

    Interface SAS data views contain descriptor information for data formatted by other software products, for example, a database management system. You access database views using the SAS/ACCESS LIBNAME statement. For more information, see SAS/ACCESS for PC Files: Reference and SAS/ACCESS for Relational Databases: Reference .

SAS Catalogs (Member Type: Catalog)

A SAS catalog is a special type of SAS file that can contain multiple entries. You can keep different types of entries in the same SAS catalog. For example, the Sasuser.Profile catalog contains funtion key definitions, fonts for graphic applications, some of your selections from the Preferences dialog box, and other information from interactive windowing procedures. SAS catalogs have a file extension of .sas7bcat.

If you want to use SAS 9.1 to access catalogs created with earlier releases of SAS for Windows, you must first convert the catalogs from the earlier releases to the SAS 9.1 format before you can use them in a SAS 9.1 program.

For more information on how to convert SAS catalogs, see Moving and Accessing SAS Files .

SAS Stored Compiled Data Step Programs (Member Type: Program)

A stored compiled DATA step program is a SAS file that contains a DATA step program that has been compiled and then stored in a SAS data library. You can execute compiled DATA step programs as needed, without having to recompile them. SAS stored compiled DATA step programs have a file extension of .sas7bpgm.

Stored compiled programs are available for DATA step applications only. Your stored programs can contain all SAS language elements except global statements. If you do include global statements in your source program, SAS stores the compiled program but not the global statements, and does not display a warning message in the SAS log.

For more information about this type of SAS file, see SAS Language Reference: Concepts .

Access Descriptor Files (Member Type: Access)

Descriptor files created by the SAS/ACCESS LIBNAME statement have a member type of ACCESS and are used when creating interface SAS data views. Descriptor files describe the data formatted by other software products supported by SAS. For more information, see SAS/ACCESS for Relational Databases: Reference , SAS/ACCESS for PC Files: Reference and other available SAS/ACCESS documentation.




SAS 9.1 Companion for Windows
SAS 9.1 Companion for Windows (2 Volumes)
ISBN: 1590472004
EAN: 2147483647
Year: 2004
Pages: 187

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