When you read a SAS
data set or an external file, I/O is measured when input data is copied
to the buffer in memory and when it is copied from the output buffer
to the output data set.
A page is the unit of
data transfer between the storage device and memory.
Increasing the page
size can speed up execution time by reducing the number of times SAS
has to read from or write to the storage medium. You can use the CONTENTS
procedure to report the page size and the number of pages.
You can use the BUFSIZE=
system option or data set 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.
You can use the BUFNO=
system or data set option to control how many buffers are available
for reading or writing a SAS data set. By increasing the number of
buffers, you can control how many pages of data are loaded into memory
with each I/O transfer.
The product of BUFNO=
and BUFSIZE=, rather than the specific value of either option, determines
how much data can be transferred in one I/O operation. Increasing
either option increases the amount of data that can be transferred
in one I/O operation. However, the improvement in I/O comes at the
cost of increased memory consumption.