SAS Companion for the CMS Environment

Accessing an External File

To access an external file, specify its filename in a SAS statement or command. For example, this INCLUDE command accesses a file that contains SAS statements and includes it into the Program Editor window:

include 'mycode sas a'

These statements access an external file of data that is used to create a SAS data set:

data mydata;
     infile 'rawdata data b';

If you plan to use the same external file several times in your SAS program, it is more efficient to use the FILENAME statement to establish a fileref for the file. (See Advantages of Using the FILENAME Statement.) You can subsequently use the fileref to refer to the file instead of specifying the filename again.

Note: Use the CMS FILEDEF command to assign a DDname, which is also a logical name, only when you read OS/390 sequential or partitioned data sets on OS/390 disks that are accessed by shared DASD, or when you read OS/390 simulated CMS files that are identified by filemode number 4. [cautionend]

Using the FILENAME Statement to Reference External Files

A fileref that is established by a FILENAME statement or FILENAME function remains in effect until the SAS session ends, or until it is changed or deleted by a FILENAME statement that specifies the same fileref. A FILENAME statement for disk always overrides a CMS FILEDEF command for disk. When you use a FILENAME statement to assign a fileref to a disk file, the native CMS interface is used for I/O. If you use a CMS FILEDEF command to assign a fileref to a disk file, OS/390 Simulation Services (provided by CMS) are used.

CAUTION:: Do not assign different filerefs to the same physical file or use the same fileref for concurrent access. For example, if you assign a fileref to a file, then browse the file through the FSLIST window, do not attempt to go to the Program Editor window and submit a DATA step to write to the file while it is still displayed in the FSLIST window.

Advantages of Using the FILENAME Statement

There are several advantages to using the FILENAME statement to identify external files.

It is portable. The FILENAME statement is recognized by SAS under all operating environments. You can develop a SAS program under CMS and port it to another operating environment with fewer changes to your program statements than if you used the CMS FILEDEF command.
It is easier for novice CMS users to understand than the CMS FILEDEF command.
It enables you to list the filerefs that you have assigned.
It reduces processing time.
- Filerefs that are assigned by a FILENAME statement are found before filerefs that are assigned that are by a FILEDEF command.
- Filerefs that are assigned by the FILENAME statement use OS/390 Simulation only for nondisk files. Filerefs that are assigned by a FILEDEF command always use OS/390 Simulation, even for disk files.

FILENAME Statement Syntax

This section provides a brief overview of FILENAME statement syntax. For complete information about the FILENAME statement, see FILENAME. The general form of the FILENAME statement is

FILENAME fileref | _ALL_ device-type <'external-file'> <options>;

The FILENAME statement takes the following options:

fileref: is a logical name by which the external file is referenced. The fileref must begin with a letter or underscore and must contain 1 to 8 characters consisting of letters, numbers, or underscores.
_ALL_: is a reserved fileref that is used only to list or clear filerefs.
device-type: specifies the type of output or input device for the file. If device-type not specified, SAS assumes that the file is on disk.
'external-file': identifies the physical file to be associated with the fileref.
options: is a list of options that control how the file is read or written. Use a blank space to separate each option when you specify more than one. All options use a keyword=value format.

FILENAME Statement Examples

The following FILENAME statements associate the fileref MYDATA with the external file HOUSES DATA A on disk. Note that the second example is equivalent to the first, but the disk option is unnecessary.
```
filename mydata 'houses data a';
```
```
filename mydata disk 'houses data a';
```
The following FILENAME statement associates the fileref OUTDATA with the external file SOME FILE, in the FPOOL:USER3.DATA97 SFS directory.
```
filename outdata 
   'some file fpool:user3.data97';
```
The following FILENAME statement associates the fileref INDATA with the external file SURVEY MARCH on disk. If this fileref is used for output, it is written to the first R/W disk. If this fileref is used for input, the standard CMS minidisk search order is followed.
```
filename indata 'survey march';
```
The following FILENAME statement associates the fileref OUT with the virtual disk PUNCH. Any output to OUT is directed to the virtual disk PUNCH.
```
filename out punch;
```
The following FILENAME statement associates the fileref MYLIB with the tape device defined as 182.
```
filename mylib tape 'tap2' ;
```
The following FILENAME statement associates the fileref MYDIR with the SFS directory FPOOL:MYUSER.MYDIR as an aggregate external file:
```
filename mydir 'fpool:myuser.mydir';
```
The following FILENAME statement clears the association between the fileref MYDATA and any device or file, provided that the fileref was originally assigned by a FILENAME statement. CLEAR is assumed by default. However, you may state it explicitly.
```
filename mydata clear;
```
The following FILENAME statement concatenates three files. When the fileref corresponding to a list of files to be concatenated occurs in a later open-for-read operation, the data is read sequentially. When the fileref occurs in a later open-for-write operation, output is written to the first file in the list.
```
filename all
   ('mar file' 'apr file' 'may file');
```
The following FILENAME statement specifies multiple members in multiple MACLIBs. You cannot specify that output be sent to a MACLIB file.
```
filename a
   ('one maclib' 'two maclib' 'three maclib');
```

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