Sorry for the late reply.
First changeset contains an sql file with the base of the DB; after that only relatively simple stuff like new columns, a constraint or index, and every now and then a new table.
From 200 or so there are about fifty sets of which each contains the addition of an index.
Just about all sets have a precondition, and if needed a rolback.
The changesets are stored in files containing the version number of our application. On average about 4 or 6 or so changes/changesets. So all together the changes where stored into 30 different files or so, which are included in one master file.
Can't send you the source for now.
The workaround has been to re-read the current, stable state from oracle into an sql file, and use that in changeset number 1; from there we have been extending again using Liquibase.