Data Set Options under UNIX

USEDIRECTIO= Data Set Option: UNIX

Turns on direct file I/O for a library that contains the file to which the ENABLEDIRECTIO option has been applied.

Default:	Off
Valid in:	DATA step
Category:	Data Set Control
Engines:	V9, V8
UNIX specifics:	To use this option, you must also use the ENABLEDIRECTIO option in the LIBNAME statement where the libref was assigned.

Syntax
Details
	The Basics
	Ways to Turn on Direct File I/O
Examples
See Also

The USEDIRECTIO= data set option turns on direct file I/O for a data set that is listed on a DATA statement. The associated libref must have been defined with the ENABLEDIRECTIO option in the LIBNAME statement.

Using ENABLEDIRECTIO on a LIBNAME statement makes direct file I/O possible for data sets in that library. Direct I/O itself is not turned on. You must use the USEDIRECTIO= option to produce direct file I/O.

Ways to Turn on Direct File I/O

You can turn on direct file I/O in two ways:

Use both the ENABLEDIRECTIO and USEDIRECTIO= options in the LIBNAME statement:
```
libname libref-name '.' ENABLEDIRECTIO USEDIRECTIO=yes;
```
In this case, SAS uses direct file I/O on all SAS I/O data sets that are opened using the libref libref-name.
Use ENABLEDIRECTIO in the LIBNAME statement and use USEDIRECTIO= in a DATA statement:
```
libname libref-name '.' ENABLEDIRECTIO;
data libref-name.data-set-name (USEDIRECTIO=yes);
```
In this case, libref-name.data-set-name.DATA will be opened for direct file I/O. Other SAS I/O data sets referenced by libref-name will not use direct file I/O.

USEDIRECTIO= by itself has no effect. Neither of the following statements open a data set for direct file I/O:

libname libref-name '.' USEDIRECTIO=yes;
data libref-name.data-set-name (USEDIRECTIO=yes);

Examples

The following example uses the ENABLEDIRECTIO LIBNAME option to enable files that are associated with the libref test to be opened for direct I/O. The USEDIRECTIO= data set option opens test.file1 for direct I/O. test.file2 is not opened for direct I/O.

LIBNAME test'.'ENABLEDIRECTIO;
data test.file1(USEDIRECTIO=yes);
   ... more SAS statements ...
run;
data test.file2;
   ... more SAS statements ...
run;

USEDIRECTIO= Data Set Option: UNIX

Syntax

The Basics

Ways to Turn on Direct File I/O