Data Set Options for Relational Databases CAST_OVERHEAD_MAXPERCENT= Data Set Option 167
cause Teradata to perform numeric conversions. The parallelism of Teradata makes it
well suited to perform this work. This is especially true when running SAS on OS/390
(MVS) where CPU activity can be costly.
CAST= can cause more data to be transferred from Teradata to SAS, as a result of
the option forcing the Teradata type into a larger SAS type. For example, the CAST= of
a Teradata BYTEINT to SAS floating point adds seven overhead bytes to each row
transferred.
The following Teradata types are candidates for casting:
INTEGER
BYTEINT
SMALLINT
DECIMAL
DATE.
SAS/ACCESS limits data expansion for CAST= to 20 percent in order to trade rapid
data conversion by Teradata for extra data transmission. If casting does not exceed a 20
percent data increase, all candidate columns are cast. If the increase exceeds this limit,
then SAS attempts to cast Teradata DECIMAL types only. If casting DECIMAL types
only still exceeds the increase limit, data conversions are done by SAS.
You can alter the casting rules by using either the CAST= or
“CAST_OVERHEAD_MAXPERCENT= LIBNAME Option” on page 75 options. With
CAST_OVERHEAD_MAXPERCENT=, you can change the 20 percent overhead limit.
With CAST=, you can override the percentage rules:
CAST=YES forces Teradata to cast all candidate columns
CAST=NO cancels all Teradata casting
CAST= only applies when you are reading Teradata tables into SAS. It does not
apply when writing Teradata tables from SAS.
Also, CAST= only applies to SQL that SAS generates for you. If you supply your own
SQL with the explicit SQL feature of PROC SQL, you must code your own casting
clauses to force data conversions to occur in Teradata instead of SAS.
See Also
“CAST= LIBNAME Option” on page 74
CAST_OVERHEAD_MAXPERCENT= Data Set Option
Specifies the overhead limit for data conversions to be performed in Teradata instead of SAS
Valid in: DATA and PROC steps (when accessing DBMS data using SAS/ACCESS
software)
DBMS support: Teradata
Default value: 20 percent
Syntax
CAST_OVERHEAD_MAXPERCENT=<n>
