Question

I have a procedure in Sybase with the following code.

begin transaction get_virtual_acc

    UPDATE store_virtual_acc SET isProc = 1, Uid = @uid, DateReserv = getdate()  
    from store_virtual_acc (index idx_id) WHERE id = (SELECT min(id) FROM store_virtual_acc (index idx_uid) where  Uid = null and isProc = null)  

commit transaction get_virtual_acc 

The problem is that when the procedure is called multiple users concurently they can receive the same min(id) and update same row in the table with different value @uid. The result is a distortion of the data. It is necessary to achieve a result, that if the line has already selected for update a single user, the other can’t select it. Table have lock type datarows.

Tried to use a transaction-level locking as follows
set transaction isolation level 3
before the transaction begin but aplication wich call the procedure get exception
java.sql.SQLException: Your server command (family id # 0, process id # 530) encountered a deadlock situation. Please re-run your command.

I would be grateful for any help.

Answer 1

Try something like this:

begin transaction get_virtual_acc

UPDATE store_virtual_acc SET isProc = 1, Uid = @uid, DateReserv = getdate()  
from store_virtual_acc (index idx_id) WHERE id = (SELECT min(id) FROM store_virtual_acc (index idx_uid) holdlock where  Uid = null and isProc = null )  

commit transaction get_virtual_acc 

The keyword is holdlock