Good evening, gentelmen.

I have one database simultaneously accessed by few processes. All of
them are performing reading/writing. After some time all working
processes are hunging up on Db::get(). db_stat-4.2 -h /path/to/home -d
database hangs up too, but the same command w/o -h key works properly.

I'm absolutely sure, that problem is in my misunderstanding or misuse
of environment. I'm always opening it with following flags: DB_CREATE |
DB_INIT_LOCK | DB_INIT_MPOOL | DB_INIT_LOG | DB_INIT_TXN. Typical
database open command is following:

db = new Db(&__env, 0);
db->open(0, name.c_str(), 0, DB_RECNO, flags, 0);

where flags are DB_CREATE or 0. Following operation hangs:

db->get(0, &key, &data, 0);

.... in all processes that are using this db home.

What am i doing wrong?

* Mykola Stryebkov:

Have you enabled the deadlock detector?

Florian Weimer wrote:
No. What's this?

* Mykola Stryebkov:

During concurrent access to the database, deadlocks may occur. You
need to handle them in some way. The Berkeley DB reference guide
contains detailed information:

<http://www.sleepycat.com/docs/ref/transapp/deadlock.html>

Florian Weimer wrote:
Thanks, I know about deadlocks nature but very new in concurrent BDB
handling. What whould you say about using db_deadlock utility for
resolving occured deadlocks? I'm thinking about use it with -t flag.

* Mykola Stryebkov:

My databases have little contention, so I call DB_ENV->set_lk_detect
and use the internal deadlock detector which runs every time a lock
cannot be obtained.

In an environment with more substantial log contention, using a
separate lock detector thread (or the command line utility, but I try
to make my applications self-contained) is perhaps the better choice.