Descriptor Information for a SAS Data Set

The descriptor information for a SAS data set makes the file self-documenting ; that is, each data set can supply the attributes of the data set and of its variables. Once the data is in the form of a SAS data set, you do not have to specify the attributes of the data set or the variables in your program statements. SAS obtains the information directly from the data set.

Descriptor information includes the number of observations, the observation length, the date that the data set was last modified, and other facts. Descriptor information for individual variables includes attributes such as name , type, length, format, label, and whether the variable is indexed.

The following figure illustrates the logical components of a SAS data set:

Figure 27.1: Logical Components of a SAS Data Set

The following items correspond to the numbers in the figure above:

1. A SAS data view (member type VIEW) contains descriptor information and uses data values from one or more data sets.

2. A SAS data file (member type DATA) contains descriptor information and data values. SAS data sets may be of member type DATA (SAS data file) or VIEW (SAS data view).

3. An index is a separate file that you can create for a SAS data file in order to provide direct access to specific observations. The index file has the same name as its data file and a member type of INDEX. Indexes can provide faster access to specific observations, particularly when you have a large data set.