Figure 1 shows how CI free space is used to insert and delete a logical record in a KSDS or variable-length RRDS.

Figure 1. Inserting a Logical Record into a CI

Two logical records are stored in the first control interval shown in Figure 1. Each logical record has a key (11 and 14). The second control interval shows what happens when you insert a logical record with a key of 12.

1. Logical record 12 is inserted in its correct collating sequence in the CI.
2. The CI definition field (CIDF) is updated to show the reduction of available free space.
3. A corresponding record definition field (RDF) is inserted in the appropriate location to describe the length of the new record.

When a record is deleted, the procedure is reversed, and the space occupied by the logical record and corresponding RDF is reclaimed as free space.