|Overview of the SAS/ACCESS Interface to IMS|
|Three Parts of the SAS/ACCESS Interface to IMS|
The ACCESS procedure enables you to describe an IMS database to SAS 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 it to create other SAS data sets, and so on. Defining SAS/ACCESS Descriptor Files describes how to create and edit SAS/ACCESS descriptor files. IMS Data in SAS Programs presents examples of using IMS data in SAS programs, and Browsing and Updating IMS Data shows how to use the view descriptor files to update IMS 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 embedded in the software, so you are seldom aware of the engine. SAS interacts automatically with the engine when you use SAS/ACCESS view descriptors in your SAS programs, so you can use IMS 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 resources. How to Use the IMS DATA Step Interface describes these statement extensions in detail.
You might need to combine data from several sources, including IMS 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. SAS 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.
|How the IMS Engine and DATA Step Interfaces Differ|
The IMS 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 access to IMS 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 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 access to the data.
|When to Use the IMS Engine Interface|
|When to Use the IMS DATA Step Interface|
|Features Not Supported by the IMS 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 DATA Step Interface|