You can use the BUFNO= system option or data set option to control how many buffers are available for reading or writing a SAS data set. Using BUFNO= can improve execution time by limiting the number of input/output operations that are required for a particular SAS data set. However, the improvement in I/O comes at the cost of increased memory consumption. The number of buffers is not a permanent attribute of the data set and is valid only for the current step or SAS session.

A page is fixed in size when the data set is created, either to a default value or a specified value. You can use the BUFSIZE= option to control the page size of an output SAS data set. The new buffer size is permanent. After it is specified, it is used whenever the data set is processed.

The total number of bytes occupied by a data set equals the page size multiplied by the number of pages. You can use the CONTENTS procedure to report the page size and the number of pages.

The SASFILE LOAD statement opens the file, allocates the buffers, and reads the data into memory.

When a SAS data file is opened using the SASFILE statement, the data is held in memory, and is available to subsequent DATA and PROC steps or applications, until either a SASFILE CLOSE statement is executed or the SAS session ends. Though a file that is opened with the SASFILE statement can be used for subsequent input or update processing, it cannot be used for subsequent utility or output processing. If the file in-memory increases in size during processing, the number of buffers also increases.