Alternative to nested transactions

Hello all,

I'm trying to port a program from MS SQL Server which does the
following:

declare a cursor with a query for possibly update;
fetch and lock rows one by one;
release the lock in case where no update is necessary;

But, to release the lock I need to commit the transaction and if I
commit the transaction I lost the cursor.

How can I simulate nested transactions??
Or how can I simulate persistent cursors??

Any ideias??

Thanks in advance.

--
João Alfredo <joaoalf(at)dotx(dot)com(dot)br>
dotX Consultoria Serviços e Conectividade