SGIO System Option: Windows

Activates the Scatter/Gather I/O feature.

Valid in: configuration file, SAS invocation
Category: Files: SAS Files
Default: NOSGIO
Windows specifics: all


Syntax Description


specifies to activate the scatter–read / gather–write feature. The scatter–read / gather–write feature remains active until your SAS session ends.


specifies not to activate the scatter-read/gather-write feature.


The SGIO system option greatly improves I/O performance for SAS I/O files (data sets, catalogs, indexes, utility files, and other I/O files) when the PC has a large amount of RAM. Scatter-read / gather-write bypasses intermediate buffer transfers between memory and disk.
When SGIO is active, SAS uses the number of buffers that are specified by the BUFNO system option to transfer data between disk and RAM. I/O performance usually improves as the value for the BUFNO increases. Try different values of the BUFNO system option to tune each SAS job or DATA step.
The scatter-read / gather-write feature is active only for the following SAS I/O files:
  • those that contain a 4K-multiple page size (for example, 4096 or 8192) on 32–bit systems
  • those that contain a 8K-multiple page size (for example, 8192 or 16384) on 64-bit systems
  • those that were not created by using Version 6 of SAS
  • those that are accessed sequentially.
If an I/O file does not meet these criteria, SGIO is inactive for that file even though the SGIO option is specified. You can access more information about SGIO in the SGIO Usage document.