can a berkeley database be opened and accessed from multiple programs at the same time?

Question

according to the Berkeley documentation the Transactional (TS) and the Concurrent Datastore version of the Database, multiple threads may access (and change) the database.

Does this also mean that I can have 2 programs linked to the berkely 'client' and have them access the same database file without any problems?

(I ask, since for a separate database server this would be no problem of course, but in the case of Berkeley the database engine is linked long with your program)

thanks!

R

Burdened

I seem to recall that the Berkeley DB can be opened with a locking flag so that access will be synchronized. Note that this does NOT work if the Berkeley DB is being accessed over NFS (potentially by multiple hosts). – Knowlton

See oracle.com/technology/documentation/berkeley-db/db/gsg/C/… – Knowlton

pp: the documentation link you provided doesn't give an answer on this. – Burdened

Correct link: download.oracle.com/docs/cd/E17076_02/html/gsg/C/… – Lictor

This may not work for all cases, but i just stood up a Embedded GrizzlyServer/Servlet container and exposed GET/POST/DELETE Rest endpoints...i didn't get much of a performance drop. – Amersfoort

Still, I did not get any solution from any answers. Did anyone find any solution to use Berkeley DB with multiple java processes? – Toque

Answer 1

Some documentation seems to think you can use the same database concurrently from multiple processes as well as from multiple threads. Specifically:

"Multiple processes, or multiple threads in a single process, can all use the database at the same time as each uses the Berkeley DB library. Low-level services like locking, transaction logging, shared buffer management, memory management, and so on are all handled transparently by the library."

A cursory read did not shed any light on what BDB uses to control access from multiple processes, but if filesystem locks are used, access from multiple processes on a network filesystems may well be problematic.

Quantize

Could you please suggest an alternative that works fine with access from multiple processes on a network filesystem? – Alyse

Answer 2

Chapter 16: The Locking Subsystem from the reference guide looks promising.

Lictor