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SAS®9 Compatibility

Migration

CEDA Processing

CEDA (cross-environment data access) is a Base SAS feature that enables you to to process SAS files in a foreign environment automatically and transparently, but with a few restrictions. This document explains CEDA processing for foreign Version 7 and 8 files in a SAS®9 session. If these details seem overwhelming and you need a quick answer, then try the easy, interactive Compatibility Calculator instead.

See other topics if you want to process a SAS®9 file in a Version 6, 7, or 8 session, or a SAS®9 file in a different SAS®9 operating environment. For the most in-depth information, see Processing Data Using Cross-Environment Data Access (CEDA) in SAS Language Reference: Concepts in the SAS online documentation.

CEDA Is Invoked for Foreign Files Only

The SAS file format stayed basically the same across Version 7, 8, and 9. But because SAS supports compatibility, for example, in your computer architecture, SAS®9 uses CEDA to process certain Version 7 or 8 files. CEDA is only invoked for foreign files, so check the list at Are My Files Foreign in SAS®9? to be sure this topic applies to you, or run the code in the following best practice.

   options msglevel=i;

   INFO: Data file MYFILES.GRADES.DATA is in a format that
   is native to another host, or the file encoding does
   not match the session encoding. Cross Environment Data
   Access will be used, which might require additional CPU
   resources and might reduce performance.

Restrictions for CEDA

Take careful note of the following processing restrictions:

• CEDA does not support DATA step views, SAS/ACCESS views that are not for Oracle or SYBASE, SAS catalogs, stored compiled DATA step programs, item stores, DMDB files, FDB files, or any SAS file that was created before SAS 7.
  
  
• Update processing is not supported.
  
  
• Indexes are not supported. Therefore, WHERE optimization with an index is not supported.
  
  
• Integrity constraint information is not available.
  
  
• An audit trail file cannot be updated, but the information is available.
  
  
• CEDA is supported only for directory-based file systems (UNIX, Windows, and OpenVMS Alpha). On OS/390 or z/OS, only HFS or zFS (UNIX files systems) libraries support CEDA. In particular, CEDA is not supported for bound libraries on OS/390 or z/OS. For additional information, see "Library Implementation Types for Base and Sequential Engines" in the z/OS Companion.
  
  
• Because the Base SAS engine translates the data as the data is read, multiple procedures require SAS to read and translate the data multiple times. In this way, the translation could affect system performance. So even if your file types are supported by CEDA, you might find the performance loss undesirable and prefer to migrate files to SAS®9.
  
  
• If a foreign data set is damaged, CEDA cannot process the file in order to repair it. CEDA does not support update processing, which is required in order to repair a damaged data set. To repair the foreign file, you must move it back to its native environment. For information on how to repair a damaged data set, see the REPAIR statement in the DATASETS procedure in Base SAS Procedures Guide.
  
  
• Transcoding could result in character data loss when encodings are incompatible. For information about encoding and transcoding, see the SAS National Language Support (NLS): Reference Guide.
  
  
• Loss of precision can occur in numeric variables when you move data between operating environments. If a numeric variable is defined with a short length, you can try increasing the length of the variable. Full-size numeric variables are less likely to encounter a loss of precision with CEDA. For more information, see "Numeric Precision in SAS Software" in SAS Language Reference: Concepts.
  
  
• Numeric variables have a minimum length of either 2 or 3 bytes, depending on the operating environment. In an operating environment that supports a minimum of 3 bytes (such as Windows or UNIX), CEDA cannot process a numeric variable that was created with a length of 2 bytes (for example, in z/OS).

Default Output for Data Representation and Encoding

For output processing that replaces an existing SAS data file, here is the default behavior. See "SAS File Processing with CEDA" in the online documentation for behavior of the SOCKET (a TCP/IP port engine in SAS/CONNECT) and TAPE engines.

Data representation

The BASE engine uses the data representation of the native environment, except with the COPY procedure, which by default uses the data representation of the file being copied. To override the default behavior, see SAS documentation about the OUTREP option. This is a data set option and a LIBNAME statement option.

Encoding

• The BASE engine uses the encoding of the existing file; that is, the encoding is cloned.

• With the BASE engines, the COPY procedure uses the encoding of the file from the source library (that is, the file being copied), regardless of whether the file existed in the target library.

See the SAS National Language Support (NLS): User's Guide for language elements that override the default encoding.