For recording RBA changes, you must calculate how many records there are in the data being shifted or moved, so you can keep track of the new RBA for each. If all the records are the same length, you calculate the number by dividing the record length into the number of bytes of data being shifted. If record length varies, you can calculate the number by using a table that not only identifies the records (by associating a record's key with its RBA), but also gives their length.

You should provide a routine to keep track of RBA changes caused by control interval and control area splits. RBA changes that occur through keyed access to a key-sequenced data set must also be recorded if you intend to process the data set later by direct-addressed access.