Normally when a DB transaction is blocked on a lock request, it must wait until the requested lock becomes available before its thread-of-control can proceed. However, it is possible to configure a transaction handle such that it will report a deadlock rather than wait for the block to clear.

You do this on a transaction by transaction basis by specifying DB_TXN_NOWAIT to the DbEnv::txn_begin() method.

For example:

    DbTxn *txn = NULL;
    try {
        envp->txn_begin(NULL, &txn, DB_TXN_NOWAIT);

        ...
    } catch (DbException &de) {
        // Deadlock detection and exception handling omitted
        // for brevity
        ...