Environment DB_PRIVATE flag

Question

Hello
I've got a question: Is it possible to open several process-private environments that would share their regions, i.e. would have the same effect as opening the environment in some directory but would not create any files?
And one more question: Do I have to enable locking if I have concurrent accesses to the environment, but not to the underlying databases. I mean, is access to the memory pool and other environment regions already synchronized, without specifying DB_INIT_LOCK?
Thanks, Giorgi.
Edited by: _Hitman47 on Dec 10, 2010 1:53 AM                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           

Answer 1

Yeah, I've read documentation. My question was following: Can I open several private environment handles per process (one per thread) which would use the same memory pool? I can make a private environment handle thread safe by specifying DB_THREAD flag and use that single handle in all threads, but performance overhead of using DB_THREAD flag is quite big - about 10%.
My idea is to use one environment handle per thread, with only DB_THREAD and DB_PRIVATE flags specified, but those environment handles MUST use the same memory pool.
In my application, each thread opens a set of databases, do some operations on them and close them. My application guarantees that no database will be opened simultaneously by more than one thread at one moment of time.
The problems begin when one thread opens a database in its own private environment, which has been previously opened(and closed!) by another thread. It seems that closing database in environment still leaves some pages unflushed to hard disk, even after calling DB_ENV->memp_sync() function. So when another thread tries to load that database, ot is not consistent and errors start to appear. If I use one single private environment handle for all threads, or open nonprivate(file-backed) environment handles in each thread, the application works as it should.
I hope I expressed myself clear enough.
Thanks, Giorgi.