Fixed-length column-store cannot store timestamps on disk, which means it cannot support writing prepare operations to disk and other similar semantics.

Given the intended use of fixed-length column-store, a reasonable approach might be to implement "standard" semantics in-memory (including support for rollback-to-stable of the in-memory state), but only write values to stable storage that are both locally durable and cannot be rolled back to an earlier state by rollback-to-stable.

alexander.gorrod, vamsi.krishna, michael.cahill, tagging you as the most likely folks to have strong opinions.