| SAS/ACCESS Interface to CA-DATACOM/DB: Reference |
Among the factors that affect the
interface performance are the size
of the table being accessed, the number of fields being accessed, and the
number of data records qualified by the selection criteria. For tables that
have many fields and many data records, you should evaluate all SAS programs
that need to access the table directly. In your evaluation, consider the
following questions:
- Does the program need all the CA-DATACOM/DB fields?
If not, create and use an appropriate view descriptor that includes only
the fields needed.
- 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" on page 74 for
circumstances in which extracting data is the more efficient method.
- Do the records need to be in a particular order? If so, include
a SORT clause in the appropriate view descriptors or a SAS BY clause in a
SAS program.
- Do the selection criteria allow CA-DATACOM/DB to use key (indexed)
fields and non-indexed fields efficiently? See WHERE Clause in a View Descriptor for some guidelines on specifying efficient
selection criteria.
- Does your WHERE clause cause CA-DATACOM/DB to
create a temporary index, which often requires excessive processing time?
For more information on displaying WHERE clauses and messages about creating
temporary indexes, see DDBTRACE= Data Set Option.
- What kind of locking mechanism is required? (See
Locks and the Spool File.)
- Are your CA-DATADICTIONARY elements well-matched to your view
descriptors?
- Would a different URT help?
- Would use of a default key give you a faster
result?
Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
