There are different ways ancillary data can be transformed. If the ancillary data is implemented as another “blockchain” DIDO, then the ancillary data is stored within another, parallel ledger and then, naturally, the transforms would be accomplished using that ledger stack’s transactions.
However, another mechanism available to transform the ancillary data is operational transformation (OT). These are similar to transactions but there can be multiple changes made to the data at the same time by multiple parties. Ancillary data using operational transforms is not necessarily immutable.