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BUFSIZE=

Language element:	data set option
Default:	none
Engines:	V6, V7, V8, V6TAPE, V7TAPE, V8TAPE
Valid as:	data set option, SAS system option
OpenVMS specifics:	integer range

integer

can range from 0 to the host maximum under OpenVMS. The engine tries to use a value in the range of 8,192 to 32,768 if possible. Specify values for BUFSIZE= in increments of 512.

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; under OpenVMS, it is always a multiple of 512 bytes. 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 integer is too large, disk space may 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 CACHESIZ= 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 CACHESIZ= and BUFSIZE= options together, see CACHESIZ=.

See Also

• BUFSIZE= data set option in SAS Language Reference: Dictionary

• Data set option: CACHESIZ=

• Setting Larger Buffer Size for Sequential Write and Read Operations

• System option: BUFSIZE=

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