SAS System Options

IBUFSIZE= System Option

Specifies the buffer page size for an index file.

Valid in:	configuration file, SAS invocation, OPTIONS statement, SAS System Options window
Category:	Files: SAS Files
PROC OPTIONS GROUP=	SASFILES
Restriction:	Specify a page size before the index file is created. After it is created, you cannot change the page size.

Syntax
Syntax Description
Details
See Also

Syntax

IBUFSIZE=n | nK | nM | nG | nT | hexX | MAX

specifies the page size to process in multiples of 1 (bytes); 1,024 (kilobytes); 1,048,576 (megabytes); 1,073,741,824 (gigabytes); or 1,099,511,627,776 (terabytes). For example, a value of 8 specifies 8 bytes, and a value of 3k specifies 3,072 bytes.

The default is 0, which causes SAS to use the minimum optimal page size for the operating environment.

hexX

specifies the page size as a hexadecimal value. You must specify the value beginning with a number (0-9), followed by an X. For example, the value 2dx sets the page size to 45 bytes.

MAX

sets the page size for an index file to the maximum possible number. For IBUFSIZE=, the value is 32,767 bytes.

Details

An index is an optional SAS file that you can create for a SAS data file in order to provide direct access to specific observations. The index file consists of entries that are organized into hierarchical levels, such as a tree structure, and connected by pointers. When an index is used to process a request, such as for WHERE processing, SAS does a search on the index file in order to rapidly locate the requested records.

Typically, you do not need to specify an index page size. However, the following situations could require a different page size:

The page size affects the number of levels in the index. The more pages there are, the more levels in the index. The more levels, the longer the index search takes. Increasing the page size allows more index values to be stored on each page, thus reducing the number of pages (and the number of levels). The number of pages required for the index varies with the page size, the length of the index value, and the values themselves. The main resource that is saved when reducing levels in the index is I/O. If your application is experiencing a lot of I/O in the index file, increasing the page size might help. However, you must re-create the index file after increasing the page size.
The index file structure requires a minimum of three index values to be stored on a page. If the length of an index value is very large, you might get an error message that the index could not be created because the page size is too small to hold three index values. Increasing the page size should eliminate the error.

Note: Experimentation is the best way to determine the optimal index page size. [cautionend]

	"Understanding SAS Indexes" in SAS Language Reference: Concepts.
	IBUFNO= System Option

IBUFSIZE= System Option

Syntax

Syntax Description