Andreas,
size between checkpoints, size of all wal's can be higher, see wal_keep_segments.
Hm, I also thought, but after looking at the source <https://github.com/postgres/postgres/blob/REL_10_STABLE/src/backend/access/transam/xlog.c#L2224>, it seems like this is a restriction on all files in pg_wal.
----- Pavel Luzanov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
