A fixed-length RRDS consists of several fixed-length slots. A fixed-length RRDS is defined using NUMBERED and a RECORDSIZE whose average and maximum lengths are the same.

Each slot has a unique relative record number, and the slots are sequenced by ascending relative record number. Each record occupies a slot and is stored and retrieved by the relative record number of that slot. The position of a data record is fixed; its relative record number cannot change. A fixed-length RRDS cannot have a prime index or an alternate index.

Because the slot can either contain data or be empty, a data record can be inserted or deleted without affecting the position of other data records in the fixed-length RRDS. The record definition field (RDF) shows whether the slot is occupied or empty. Free space is not provided in a fixed-length RRDS because the entire data set is divided into fixed-length slots.

In a fixed-length RRDS, each control interval contains the same number of slots. The number of slots is determined by the control interval size and the record length. Figure 1 shows the structure of a fixed-length RRDS after adding a few records. Each slot has a relative record number and an RDF. Table 1 shows the access options available for RRDS processing.

Figure 1. Fixed-length relative-record data set