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.
Operation | Sequential Access | Direct or Skip- Sequential Access |
---|---|---|
Loading the data set | Yes | Yes |
Adding records | Yes (empty slots are used) | Yes (empty slots are used) |
Retrieving records | Yes | Yes (by relative record number) |
Updating records | Yes | Yes |
Deleting records | Yes (a slot given up by a deleted record can be reused) | Yes (a slot given up by a deleted record can be reused) |