> With Firebird, it can't happen. Your reports will ALWAYS run.
>
> (just a rambling snippet from my experience)

This is not necessarily true. Here is a sure-fire way to block a db/table:

1. Start IBExpert
2. Enter data grid and modify a value in one of the cells
3. Hit the check mark icon in the grid (not the transaction commit button)
4. DO NOT COMMIT the transaction at this time
5. Start a separate application that will use ADO and OleDB driver to
read the table that you just modified
6. ADO application hangs until you commit transaction in IB Expert.

The strange thing is that this only happens with IBExpert. But
nevertheless it is possible to block readers.