Differences between Data Files and SAS Views

A SAS data file is a type of SAS data set that contains both descriptor information about the data and the data values themselves. SAS views contain only descriptor information and instructions for retrieving data that is stored elsewhere. Once the data is retrieved by SAS, it can be manipulated in a DATA step.

When you reference a data file in a later PROC step, you see the data values as they were when the data file was created or last updated. When you reference a SAS view in a PROC step, the view executes and provides an image of the data values as they currently exist, not as they existed when the view was defined.

SAS views cannot be stored on tape. Because of their dynamic nature, SAS views must derive their information from data files on random-access storage devices, such as disk drives. SAS views cannot derive their information from files stored on sequentially accessed storage devices, such as tape drives.

You cannot write to a SAS view, but some SQL views can be updated.

The audit trail is an optional SAS file that logs modifications to a SAS data file. Each time an observation is added, deleted, or updated, information is written to the audit trail about who made the modification, what was modified, and when.

Generations provide the ability to keep multiple copies of a SAS data file. The multiple copies represent versions of the same data file, which is archived each time it is replaced.

When you update a SAS data file, you can ensure that the data conforms to certain standards by using integrity constraints. With SAS views, you can assign integrity constraints to the data files that the views reference.

Indexing might enable SAS to find data in a SAS data file more quickly. SAS views cannot be indexed.

Encryption provides an extra layer of security to physical files. SAS views cannot be encrypted.

Compression makes it possible to store physical files in less space. SAS views cannot be compressed.