Larry Knibb wrote: > On 15 October 2012 12:32, Keith Medcalf <kmedc...@dessus.com> wrote: >> Define "clients". Do you mean multiple client processes running on a single >> computer against a database hosted on an attached local device, such as on a >> Terminal Server for example? Or do you mean multiple clients connecting >> over LANMAN/CIFS/NFS to a database file sitting on a remote fileserver? > > It's the second one. The database file is being accessed over the network. > >> If file locking is working correctly, you cannot have multiple writes to a >> database. Write operations to the database are exclusive. > > As Simon correctly guessed, the database isn't actually being > corrupted; I'm just getting an error that suggests that it is. So I
Maybe it is not really corrupted now, but if 1) locking is not working properly (when database file is on networked fs), and 2) two writers will modify db at same time, you *will* corrupt your database. > suspect the writes are not conflicting, but one is failing (possibly) > due to another happening at the same time and whatever locking/waiting > not being observed properly results in this 'malformed' error rather > than a blocking error. > >> You may wish to try forcing locks to be acquired sooner when updating the >> database by using BEGIN IMMEDIATE or perhaps even BEGIN EXCLUSIVE before >> updating the database, and COMMIT when you are done. You will then also >> need a busy-timeout so that other readers/writers will wait for that >> operation to complete. You can set the timeout when creating the connection >> with sqlite3 in python, or by using PRAGMA busy_timeout > > Thanks - I'll give that a shot. > >> Latency of locking operations over network connections can play havoc, >> however. It is possible if you are using a network mounted database file >> that the write operations are not being flushed properly and or the locks >> are not propagating in a timely fashion. >> >> http://www.sqlite.org/lang_transaction.html >> http://www.sqlite.org/lockingv3.html > > Reading up now... _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
