On: SQLite: Wal2 Mode

[nbevans]

There is a .shm (shared memory) file that all SQLite connections to the database would use to determine which page ranges are in the WAL versus main DB file. So that overhead already exists when WAL is enabled.

[rmbyrro → nbevans]

I'm not familiar with its inner workings, but if there were n WAL files, I'd expect the overhead to be a function of n.

[dspillett → rmbyrro]

Possibly a bad function of n (linear or worse) on IO systems based on traditional drives or dirt cheap SSDs, once IO becomes your main bottleneck (i.e. when you data no longer fits easily in RAM).