Not really. It's often all just shared memory via mmap. The files are never closed, and sometimes never operated on with read/write because they're just mapped.

Not really. It's often all just shared memory via mmap. The files are never closed, and sometimes never operated on with read/write because they're just mapped. This behavior is common between (eg) both sqlite and mysql. (Postgres defaults otherwise, but architecturally it is not different) The visibility issues you're raising, basically implementing views and transactions, would not be applicable to any of these systems. You're confusing durability guarantees (fsync, msync) with visibility guarantees -- the latter of which are just standard memory access issues.