Using Data Set Options

Most SAS data set options can apply to either input or output SAS data sets in DATA steps or procedure (PROC) steps. If a data set option is associated with an input data set, the action applies to the data set that is being read. If the option appears in the DATA statement or after an output data set specification in a PROC step, SAS applies the action to the output data set. In the DATA step, data set options for output data sets must appear in the DATA statement, not in any OUTPUT statements that might be present.

Some data set options, such as COMPRESS=, are meaningful only when you create a SAS data set because they set attributes that exist for the duration of the data set. To change or cancel most data set options, you must re-create the data set. You can change other options (such as PW= and LABEL=) with PROC DATASETS. For more information, see DATASETS Procedure in Base SAS Procedures Guide.

When data set options appear on both input and output data sets in the same DATA or PROC step, first SAS applies data set options to input data sets. Then SAS evaluates programming statements or applies data set options to output data sets. Likewise, data set options that are specified for the data set being created are applied after programming statements are processed. For example, when using the RENAME= data set option, the new names are not associated with the variables until the DATA step ends.

In some instances, data set options conflict when they are used in the same statement. For example, you cannot specify both the DROP= and KEEP= data set options for the same variable in the same statement. Timing can also be an issue in some cases. For example, if using KEEP= and RENAME= on a data set specified in the SET statement, KEEP= needs to use the original variable names. SAS processes KEEP= before the data set is read. The new names specified in RENAME= apply to the programming statements that follow the SET statement.

Many system options and data set options share the same name and have the same function. System options remain in effect for all DATA and PROC steps in a SAS job or session.

The data set option overrides the system option for the data set in the step in which it appears. In this example, the OBS= system option in the OPTIONS statement specifies that only the first 100 observations are processed from any data set within the SAS job. The OBS= data set option in the SET statement, however, overrides the system option for data set TWO and specifies that only the first five observations are read from data set TWO. The PROC PRINT step prints the data set FINAL. This data set contains the first 5 observations from data set TWO, followed by the first 100 observations from data set THREE:

options obs=100;    

data final;
   set two(obs=5) three;  
run;

proc print data=final; 
run;