Data Set Options under OpenVMS

BUFSIZE= Data Set Option: OpenVMS

Specifies the size of a permanent buffer page for an output SAS data set.

Default:	none
Valid in:	DATA step and PROC steps
Category:	Data Set Control
Engines:	V9, V8, V7, V9TAPE, V8TAPE, V7TAPE
OpenVMS specifics:	the value of n
See:	BUFSIZE= Data Set Option in SAS Language Reference: Dictionary

Syntax
Details
See Also

Syntax

BUFSIZE=n | nK | nM | nG | hexX | MAX

n | nK | nM | nG

specifies the page size in multiples of 1 (bytes); 1,024 (kilobytes); 1,048,576 (megabytes); or 1,073,741,824 (gigabytes). For example a value of 4k specifies a page size of 4096 bytes.

Note: When you specify n, the value should be in increments of 512. However, the n in nK, nM, and nG does not need to be in increments of 512. [cautionend]

hexX

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

MAX

sets the buffer page size to the maximum possible number in your operating environment, up to the largest four-byte, signed integer, which is 2³¹-1, or approximately 2 billion bytes.

Details

The BUFSIZE= data set option specifies the page size (in bytes) for SAS files. A page of a data set is a logical unit that is used by the engine. The page size is a permanent attribute of the data set. The page size is set when the file is created and cannot be changed thereafter. There is no default value; the value that the engine uses depends on the size of the observation.

For efficiency, use a larger BUFSIZE= value because it reduces the number of I/Os required to read or write the file. However, if the value is too large, disk space could be wasted. Pages must be written in full, even if they are only partially full of data. This means that if you set BUFSIZE= to a large value, 65,536 for example, and the last page contains only 4,000 bytes of data, more than 61,000 bytes of unused storage are written to disk, consuming approximately 120 disk blocks unnecessarily.

The system-dependent CACHESIZE= data set option is related to the BUFSIZE= data set option and can improve I/O performance without wasting disk space. For information about using the CACHESIZE= and BUFSIZE= options together, see CACHESIZE= Data Set Option: OpenVMS.