public PutOutcome put(final Txn<ByteBuffer> writeTxn,
                          final ByteBuffer keyBuffer,
                          final ByteBuffer valueBuffer,
                          final boolean overwriteExisting) {
        return put(writeTxn, keyBuffer, valueBuffer, overwriteExisting, false);
    }
This will fail if you are already inside a txn.
stroom-lmdb/src/main/java/stroom/lmdb/AbstractLmdbDb.java