Defining SAS/ACCESS Descriptor Files

SAS/ACCESS Descriptor Files Essentials

One way that SAS interacts with IMS databases is through an interface view engine that makes use of SAS/ACCESS descriptor files created with the ACCESS procedure. There are two types of descriptor files:

access descriptors
view descriptors

An access descriptor contains information about the IMS database that you want to use. The information includes the IMS database name, the IMS field names and their default SAS formats, database formats, segment names and lengths, and key fields. An access descriptor also contains any special handling considerations for a field and indicates if an item occurs multiple times in a database segment. You use the access descriptor to create view descriptors. An access descriptor is like a master descriptor file for a single IMS database because it contains a complete description of that database (if you choose to enter all the data). Because IMS does not store descriptive information about a database, you must enter the database definition in the access descriptor.

A view descriptor defines a subset of the data that is described by an access descriptor.

Note: This subset must contain data from only one path in the database on which the access descriptor is based. You choose this subset by selecting particular items and specifying criteria that the data must meet. [cautionend]

For example, you might want to select two items, CUSTOMER_NAME and STATE, and specify that the value stored in item STATE must equal NC .

A view descriptor is a SAS data set of member type VIEW. After you create your view descriptors, you can use them in a SAS program to read or write the data directly from and to an IMS database, or you can extract IMS data and place it in a SAS data file. Typically, you have several view descriptors (each selecting a different path of data in the database) for each access descriptor that you have defined.

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