Hi, thanks for the response. I'm still unclear though. Can you please clarify what the xShm* VFS operations are supposed to do: xShmMap, xShmLock and SQLITE_SHM_NLOCK, xShmBarrier and xShmUnmap.
I'd suppose Sqlite uses the latter three as functional equivalent to mutexes to guarantee state/data consistency in parallell access to the mapped memory? And furthermore, by shared memory in this scope, do we mean a memory allocation that is shared between apps (without a mirror on disk), or, do we mean a disk file where the OS provides a conveniency wrapper for fread and fwrite such that the app can now do this by accessing a particular interval or memory addresses instead. In all cases, does Sqlite access the shared memory file via direct RAM access (e.g. mov [address],ax) or via fread/fwrite? If I remember right, previously on the ML, a person said that a WAL database could be opened by several nodes on a networked filesystem simultaneously. I'd like to be able to understand if this is correct or not - need to understand what the xShm* and foundation for the mapping as per above is for this though. Thanks and kind regards, Mikael 2012/1/29 Roger Binns <rog...@rogerbinns.com> > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 28/01/12 02:17, Mikael wrote: > > I have a hard time getting a clue of how exactly sqlite uses them, > > WAL is well documented at: > > http://www.sqlite.org/wal.html > > The latest major section talks about shared memory and the wal-index. It > also includes a link to more details about the wal-index which points here: > > http://www.sqlite.org/fileformat2.html#walindexformat > > Roger > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.11 (GNU/Linux) > > iEYEARECAAYFAk8km4EACgkQmOOfHg372QSKVQCgn3p/I1acLmBCScAItsUnSaEB > V/4AoMsDQfEgtJKP4eHYVtXzgO+bezj5 > =EZ52 > -----END PGP SIGNATURE----- > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
