Previous Page | Next Page

Overview of the SAS/ACCESS Interface to IMS

SAS/ACCESS Descriptor Files for IMS

Using SAS/ACCESS Descriptor Files

SAS/ACCESS descriptor files are the tools that the SAS/ACCESS interface view engine uses to establish a connection between SAS and IMS. To create these files, you run the ACCESS procedure using one of three methods:

There are two types of descriptor files: access descriptors and view descriptors. They are discussed in the next two sections. The following figure illustrates the relationships among an IMS database, an access descriptor, and view descriptors. Defining SAS/ACCESS Descriptor Files shows you how to create, browse, and edit these files.

Relationships between an IMS Database, an Access Descriptor, and View Descriptors

[Relationships among an IMS-DL/I Database, an Access Descriptor, and View Descriptors]

Access Descriptor Files

Access descriptor files are of member type ACCESS. Each access descriptor holds essential information about the IMS database that you want to access, for example, the name of the database; the names of segments, search fields, and key fields; segment lengths; names of non-search fields in the database; and data types. An access descriptor might also contain the corresponding SAS information, such as the SAS variable names and formats. Typically, you have only one access descriptor for each IMS database.

Since an access descriptor describes only one IMS database, you cannot create a single access descriptor that accesses multiple physical IMS databases; however, you can create a single access descriptor for a logical IMS database that accesses multiple physical databases.

View Descriptor Files

View descriptor files are sometimes called views because their member type is VIEW. This document uses the term view descriptors to distinguish view descriptor files from views created by the SAS SQL procedure or a DATA step.

Each view descriptor can define all the data in one path of the database, or a particular subset of the data in one path of the database (see IMS Essentials for a discussion of paths and other IMS concepts). View descriptors enable you to define all the data in one path of the database by selecting the items that you want to use and specifying selection criteria for only the records that you want. For example, you might want only records with a transaction date of July 3, 1995, and for customers who live in Richmond. You might have several view descriptors, each selecting different paths of data in an access descriptor that you have defined. You might also have view descriptors that select different subsets of data in one path of an access descriptor.

You can join data by using SAS's SQL procedure. With the SQL procedure, you can create a view that joins and summarizes data from multiple view descriptors (based on IMS databases), SAS data files, DATA step views, or other PROC SQL views. See IMS Data in SAS Programs for a discussion and examples that use the SQL procedure.

Previous Page | Next Page | Top of Page