| SAS/ACCESS Interface to IMS-DL/I Software |
The SAS/ACCESS interface
to IMS-DL/I consists of three parts:
- the ACCESS procedure, which you use to define
the SAS/ACCESS descriptor files
- the IMS-DL/I interface view engine, which enables
you to use IMS-DL/I descriptor files in SAS programs in much the same way
you use SAS data files
- the DATA step interface, which enables you to
access information in IMS-DL/I databases using SAS programming statements.
The ACCESS
procedure enables you to describe an IMS-DL/I database to the SAS System in
an access descriptor file. You can then create view descriptor files from
the access descriptor file, which you can use in SAS programs in much the
same way as you would use SAS data files. You can print, plot, and chart
the data described by the view descriptor files, use them to create other
SAS data sets, and so on. Defining SAS/ACCESS Descriptor Files
describes how to create and edit SAS/ACCESS descriptor
files. Using IMS-DL/I Data in SAS Programs
presents examples of using IMS-DL/I data in SAS programs, and Browsing and Updating IMS-DL/I Data shows how to use the view
descriptor files to update IMS-DL/I data from within a SAS program.
The interface view engine is an integral part of the SAS/ACCESS interface,
but the interface's design is transparent, so you are seldom aware of the
engine. The SAS System interacts automatically with the engine when you use SAS/ACCESS view
descriptors in your SAS programs, so you can use IMS-DL/I data in your programs
in much the same way as you use SAS data.
The DATA step interface provides special extensions of standard SAS INFILE
and FILE statements to access IMS-DL/I resources. Using the SAS/ACCESS Interface to IMS-DL/I DATA Step Interface
describes these statement extensions in detail.
You may need to combine data from several sources, including
IMS-DL/I databases, Version 6 SAS data sets, Version 7 SAS data sets, and
other databases. With the SAS/ACCESS interface, such combinations are not
only possible, but easy to do. The SAS System can differentiate among SAS
data sets, SAS/ACCESS view descriptor
files, and other types of SAS files, and it can use the appropriate access
method.
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| How the IMS-DL/I Engine and DATA Step Interfaces Differ |
When comparing the two interfaces, you can identify some obvious
differences:
- The IMS-DL/I interface view engine requires you
to create descriptor files. The engine uses information from the descriptor
files to successfully attach IMS and retrieve or update the data being requested
by the application. The DATA step interface requires no such files since it
is a programming interface.
- The engine access method provides transparent
access to IMS-DL/I data. To access data, you simply make reference to a descriptor
file and you have access to the data defined by the view. Coding DATA step
programs requires in-depth knowledge of the database that is being accessed,
and the ability to code host level calls to retrieve or update IMS-DL/I data.
You can, however, create SAS DATA step views from the DATA step programs to
provide users who are unfamiliar with the DL/I language transparent access
to the data.
When to Use the IMS-DL/I Engine Interface
Use the IMS-DL/I engine interface for:
- transparent access to IMS-DL/I
data
- access to data that lie in a single database path.
Performance is enhanced when SSAs can be generated from WHERE statements.
- assigning READ/WRITE/ALTER levels of protection
with passwords.
When to Use the IMS-DL/I DATA Step Interface
Use the IMS-DL/I DATA step interface for:
- programs that need full
control over DBMS access.
The DATA step interface provides total CHKP control in an update program as
well as control over DBMS calls and SSAs.
- transaction-style programs that need the capability
of dynamically generating SSAs from SAS variable values in transaction files.
- multi-path processing or accessing data from multiple
databases in the same application. Joining data can be more efficient when
performed in the DATA step as opposed to the engine interface.
- access to message queues in a BMP region.
- access to
Fast Path databases.
Features Not Supported by the IMS-DL/I Engine Interface
The engine does not support Fast Path,
message queue access,
or HSSR. The SLI region type is also no longer supported; however, you can
use the DBCTL feature of IMS/ESA and CICS/ESA for those functions.
Features Not Supported by the IMS-DL/I DATA Step Interface
The DATA step does not support the DLITEST procedure and HSSR.
The SLI region type is also no longer supported; however, you can use the
DBCTL feature of IMS/ESA and CICS/ESA for
those functions.
Copyright 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
