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Ways of Allocating External Files

To work with an external file in the SAS System, you must first allocate the file. File allocation is the process of identifying an external file to the SAS System. If you are allocating a new data set, such as a sequential file, partitioned data set (PDS), or partitioned data set extended (PDSE), you must specify that it is new and you must describe its structure and format. These actions are not required for new files in the Hierarchical File System (HFS).

You can allocate external files in the following ways:

• If you plan to use an existing external file only once in your SAS program, then you can allocate it by simply specifying the physical file name in a SAS statement or command. For example, this INCLUDE command allocates an existing sequential data set and includes it into the PROGRAM EDITOR window:

  include 'myid.report.data'

  Similarly, this PROC PRINTTO statement allocates a new PDS member:

  proc printto 
     print='userid.output.data(rockport)'
     new;

• If you plan to use the same external file several times in your SAS program, then use one of the following methods to allocate the file.

  SAS FILENAME statement or function

  You can use these methods in all modes for most types of files. See Using the FILENAME Statement or Function to Allocate External Files or FILENAME for more information.

  JCL DD statement

  You can use this method if you use OS/390 in batch mode. See Using the JCL DD Statement to Allocate External Files for more information.

  Note:   Unlike the other two methods, if you use the JCL DD statement to allocate a file, there is no way to deallocate the file until the job ends.  
  

  TSO ALLOCATE command

  You can use this method if you use OS/390 under TSO. See Using the TSO Allocate Command to Allocate External Files for more information.

  Each of these methods establishes a fileref or a DDname that you can subsequently use to refer to the file instead of specifying the data set name again. See Referring to External Files for more information.

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