Topics:

• The Retrieval Subtree
• Retrieval Sequence
• Effects of Screening Conditions on Retrieval
• Retrieving Short Paths
• File Inversion
• The JOIN Command

This chapter explains how your Master File is used to select segments and retrieve data from them. It also discusses:

• How screening conditions (IF criteria) improve I/O efficiency.
• Unique and non-unique segments with short paths.
• How you can change retrieval logic by specifying a new root segment.
• How you can join structures together for reporting purposes.

The examples in this chapter reference the EMPFULL Master and Access Files. Creating File Descriptions With AUTOIDMS, contains a sample session that demonstrates how to create the EMPFULL Master and Access Files. For a complete listing of these file descriptions, see Adapter for CA-IDMS Samples.

Note: The term record refers to a record occurrence; it should not be confused with the IDMS term record-type.

Topics pertaining to unique segments discuss considerations/implications that are true regardless of whether the unique segment is an owner of its parent or related to it through a CALC field, index, or LRF field.