Two-pass processing occurs when a SAS
Teradata requests that data be made available for multiple pass
reading (that is, more than one pass through the data set). In the
context of DBMS engines, this requires that as the data is read from
the database, temporary spool files are written containing the read
data. There is one temporary spool file per thread, and each spool
file contains all data read on that thread. If three threads are specified
for threaded Reads, three temporary spool files are written.
As the application requests
subsequent passes of data, data is read from the temporary spool files,
not reread from the database. The temporary spool files can be written
on different disks, reducing any disk read contention, and enhancing
performance. To accomplish this, the SAS option UTILLOC= is used to
define different disk devices and directory paths when creating temporary
spool files. There are several ways to specify this option.
-
In the SAS config file, add this
line:
–utilloc("C:\path" "D:\path" "E:\path")
-
Specify the UTILLOC= option on
the SAS command line:
/* on Windows */
sas –utilloc(c:\path d:\path e:\path)
/* on UNIX */
sas –utilloc '(\path \path2 \path3)'
For more information
about the UTILLOC= SAS system option, see the
SAS System Options: Reference.