Trying a new example I found the answer to my question :

Doing an %OpenId with concurrent parameter to 4 is like Lock and Unlock right away, so then the Lock is in a state Exclusive->DeLock that means that is "waiting" for Transaction to finish to remove it, that is how it works.

I want to implement a MUTEX, so I cannot do the same. Then, my only way is to remove the lock explicitely and control all possible error ways.

Thanks to all,

Jordi