|SAS/ACCESS Interface to SYSTEM 2000 Data Management Software: Reference
Among the factors that affect SYSTEM 2000 performance are the size of
the database being accessed, the number of items being accessed, and the number
of data records qualified by the selection criteria. For databases that have
many items and many data records, you should evaluate all SAS programs that
need to access the database directly. In your evaluation, consider the following
- Does the program need all the SYSTEM 2000 items? If not, create
and use an appropriate view descriptor that includes only the items to be
- Do the selection criteria retrieve only those data records needed
for subsequent analysis? If not, specify different conditions so that the
selected records are restricted for the program being used.
- Are the data going to be used by more than one procedure in one
SAS session? If so, consider extracting the data and placing them in a SAS
data file for SAS procedures to use, instead of allowing the data to be accessed
directly by each procedure. See Performance Considerations
for circumstances when extracting data is the more efficient method.
- Do the records need to be in a particular order? If so, include
a SYSTEM 2000 ordering-clause in the appropriate view descriptors or a SAS
ORDER BY clause in a SAS program.
- Do the selection criteria allow SYSTEM 2000 software to use key
(indexed) items and non-key (not indexed) items efficiently? See SYSTEM 2000 Where-Clause for some guidelines on
specifying efficient selection criteria.
- What kind of locking mechanism will SYSTEM 2000 software need
to use? (See Levels of Locking.)
Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.