bsddb3 database file, what are the __db.001, __db.002, __db.003 files for?

[Klaas]

Claudio Grondi wrote:

> Beside the intended database file
>    databaseFile.bdb
> I see in same directory also the
>    __db.001
>    __db.002
>    __db.003
> files where
>    __db.003 is ten times as larger as the databaseFile.bdb
> and
>    __db.001 has the same size as the databaseFile.bdb .

I can't tell you exactly what each is, but they are the files that the
shared environment (DBEnv) uses to coordinate multi-process access to
the database.  In particular, the big one is likely the mmap'd cache
(which defaults to 5Mb, I believe).

You can safely delete them, but probably shouldn't while your program
is executing.

> Is there any _good_ documentation of the bsddb3 module around beside
> this provided with this module itself, where it is not necessary e.g. to
> guess, that C integer value of zero (0) is represented in Python by the
> value None returned in case of success by db.open() ?

This is the only documentation available, AFAIK:
http://pybsddb.sourceforge.net/bsddb3.html

For most of the important stuff it is necessary to dig into the bdb
docs themselves.

-Mike