Merci bcp.

Effectivement, dans la doc PB, on peut lire :

"To specify that a DataWindow object retrieve only as many rows as it
needs to:
Select Rows>Retrieve Options>Rows As Needed from the menu bar.
With this setting, PowerBuilder presents data and returns control to the
user when it has retrieved enough rows to display in the DataWindow
object.
Retrieve Rows As Needed is overridden if you have specified sorting or have
used aggregate functions, such as Avg and Sum, in the DataWindow object.
This is because PowerBuilder must retrieve every row before it can sort or
perform aggregates.
In a multiuser situation, Retrieve Rows As Needed might lock other people
from the tables."

A priori, cela devrait résoudre mon pb.