SAS Certification Prep Guide, 4th Edition

Controlling Page Size and the Number of Buffers

Measuring I/O

Improvement in I/O can come at the cost of increased memory consumption. In order to understand the relationship between I/O and memory, it is helpful to know when data is copied to a buffer and where I/O is measured. When you create a SAS data set using a DATA step, the following actions occur:

1. SAS copies a page of data from the input data set to a buffer in memory.
2. One observation at a time is loaded from the buffer into the program data vector.
3. Each observation is written from the PDV to an output buffer.
4. The contents of the output buffer are written to the disk when the buffer is full.

The process for reading external files is similar. However, each ...