What are the information stored in CI?

CI (Control Interval) consists of Record Descriptor Field (RDF) and Control Interval Descriptor Field (CIDF). Every CI will consist of one CI which consists of the last 4 bytes. This CIDF has all the information about the length of free space in CI and also the offset. If the fixed size records are used, then the every CI contains 2 RDF which is of 3 bytes each. The size of the index portion can be of 512, 1024, 2048, and 4096. The data portion in every CI should be stored in the multiples of 512 or 2048 bytes only.