CEDA
is not the preferred strategy for network file access in all situations.
CEDA has these limitations:
-
CEDA features are implemented for
SAS 9 or SAS 8 data sets, PROC SQL views,
SAS/ACCESS views for Oracle
and Sybase, and MDDBs. CEDA does not support SAS 9 or SAS 8 stored
programs or catalogs, nor does it support any SAS 6 or earlier files.
The type of access that CEDA has to a SAS file depends on the engine
used and the type of file access requested (read, write, update).
For more information about file access limitations, see
SAS File Processing with CEDA in SAS Language Reference: Concepts.
-
CEDA does not support update processing
for any SAS files.
-
CEDA does not support subsetting
by means of an index.
-
CEDA can read audit trails but
it cannot update them.
-
The processing of integrity constraints
is not supported.
-
Under
z/OS, SAS bound libraries
support only SAS data sets that have a CEDA data representation of
MVS_32. However, UNIX File System libraries on
z/OS support all CEDA
data representations.
-
Network resources are consumed
each time CEDA translates a SAS file.
-
Transcoding could result in character
data loss when encodings are incompatible. For details about encoding
and transcoding, see
SAS National Language Support (NLS): Reference Guide.
-
If a file that is in a foreign
format is damaged, it cannot be repaired because CEDA does not support
update processing, which is the strategy that you use to repair a
damaged data set. To repair the file, you must move it back to the
source environment. For details about repairing a damaged data set,
see the REPAIR statement in the DATASETS procedure in the
Base SAS Procedures Guide.
-
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). If you encounter
this restriction, use the XPORT engine or the CPORT and CIMPORT procedures
instead of CEDA.
-
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 than short numeric variables to encounter a loss of
precision with CEDA. For more information, see the topic about numeric
precision in
SAS Language Reference: Concepts.
If you have performance
problems, analyze file access patterns to determine whether the data
set is located on the correct computer. For example, if the SAS data
set is represented in UNIX data format, but most of the read operations
originate from Windows computers, you might consider moving the data
set to a Windows computer and changing the data set's UNIX file format
to Windows format. Windows access to a network-mounted file in Windows
format would not require CEDA. Changing the file's format would improve
performance and allow write and update access. However, CEDA would
be used to translate between the native Windows format of the SAS
file being accessed and the accessing computers other than Windows
(such as UNIX,
z/OS, and OpenVMS).