Overview

A SAS Data Set is a special type of file maintained by the SAS system which contains both data values and descriptive information (e.g., variable names, formats, labels) about the data. All SAS PROCs (e.g., PROC PRINT, PROC GLM) use SAS Data Sets as input.

SAS Data Sets are created during the Data Step of a SAS job. Data Steps begin with a SAS Data statement (e.g., data test;) and end with (a) another Data statement, (b) a PROC Statement (e.g., PROC MEANS), or (c) a Run statement (i.e., run;).

By default, all SAS Data Sets are deleted at the end of a batch job or Display Manager session. In order to use the SAS Data Set in future jobs/sessions, it is necessary to re-run the Data Step that created the SAS Data Set. This consumes both time and computer resources.

As an alternative to re-running a SAS Data Step at the beginning of each SAS batch job or Display Manager session, it is possible to make a SAS Data Set permanent. Permanent SAS Data Sets exist independently of the SAS job/session in which they are created. Future SAS jobs/sessions may then simply refer to the existing (i.e., permanent) SAS Data Set rather than re-create it. This saves time and resources.

Conventions

Within this document, UNIX commands that you will enter at your terminal are in Bold Courier font. Information intended to be typed into files or windows appears in boldface. Filenames and (sub)directory names are in italics.

Sample Run - Creating the Permanent SAS Data Set

Step 1:

Create a directory called mywork within your RCI or other UNIX account using the

UNIX mkdir command.

     > mkdir mywork

Step 2:

Type and submit the following SAS statements using either batch mode or the SAS Display Manager.

     libname proj1 'mywork';         
     data proj1.test;             
     input id var1 var2;
     cards;
     01 2 3
     02 4 4
     03 4 2
     04 2 1
     05 2 3
     06 3 9
     ;
     run;

The Libname statement associates the directory mywork with the name proj1. Proj1is known as a Libref. A Libref is a nickname for a physical location such as a directory (e.g., mywork).

The Data Statement instructs SAS to create a SAS Data Set test in the directory referenced by the Libref proj1 (i.e., in the mywork directory).

Step 4:

Use the UNIX ls command to look for a file named test.ssd01 in the proj1 directory.

This is the permanent SAS Data Set created with the SAS statements above.

     > ls mywork

Two Sample Runs - Using the Permanent SAS Data Set

Sample Run #1:

Later (i.e., in a different batch job, or after quitting and re-starting the SAS Display Manager), type and submit the following SAS statements.

     libname proj1 'mywork';
     proc means data=proj1.test;
     run; 

The above statements again assign proj1 as a Libref for the mywork directory and then instruct SAS to run PROC MEANS using the SAS Data Set test from the proj1 Library (i.e., from the mywork directory).

Sample Run #2

In a later SAS batch job or Display Manager session, create a new permanent SAS Data Set called newtest using the data in test.

     libname proj1 'mywork';
     data proj1.newtest;
     set proj1.test;
     var3=var1+var2;
     run;

The new permanent SAS Data Set newtest will contain the same data as test plus a new variable called "var3". Use the ls command to verify that your mywork directory now contains test.ssd01 and newtest.ssd01.

Notes

All Libref assignments (created with a Libname statement) are cancelled at the end of a SAS batch job or Display Manager session. Later SAS jobs/sessions must re-assign Librefs to the directories containing permanent SAS Data Sets before these Data Sets may be accessed.

Multiple Librefs may be established during a SAS job/session (i.e., multiple Libname statements are permitted, each linking a Libref to a directory). This is useful for storing your permanent SAS Data Sets in different locations.

Multiple SAS Data Sets may be assigned to each Libref/Library. For example, the following statements read and sort a permanent SAS Data Set called presort and save the sorted data in a permanent SAS Data Set called postsort. Both SAS Data Sets are assigned to the proj1 Library.

     libname proj1 'mywork';
     proc sort data=proj1.presort out=proj1.postsort;
        by name;