WAL mode does introduce a number of important usage limitations. https://www.vldb.org/pvldb/vol15/p3535-gaffney.pdf https://www.vldb.org/pvldb/vol15/p3535-gaff

WAL mode does introduce a number of important usage limitations. https://www.vldb.org/pvldb/vol15/p3535-gaffney.pdf https://www.vldb.org/pvldb/vol15/p3535-gaffney.pdf “To accelerate searching the WAL, SQLite creates a WAL index in shared memory. This improves the performance of read transactions, but the use of shared memory requires that all readers must be on the same machine [and OS instance]. Thus, WAL mode does not work on a network filesystem.” “It is not possible to change the page size after entering WAL mode.” “In addition, WAL mode comes with the added complexity of checkpoint operations and additional files to store the WAL and the WAL index.” https://www.sqlite.org/lang_attach.html https://www.sqlite.org/lang_attach.html “SQLite does not guarantee ACID consistency with ATTACH DATABASE in WAL mode. “Transactions involving multiple attached databases are atomic, assuming that the main database is not ":memory:" and the journal_mode is not WAL. If the main database is ":memory:" or if the journal_mode is WAL, then transactions continue to be atomic within each individual database file. But if the host computer crashes in the middle of a COMMIT where two or more database files are updated, some of those files might get the changes where others might not.”