Even when setting MashupFlight_DisableOracleBundledOdacProviderV2 value to True, the problem exists.
FetchSize in: Computer\HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\ODP.NET\4.122.19.1
(that is the unmanaged driver section)
reads 131072 on a August 2026 data gateway installed from scratch.
By changing it to 8388608, a small dataset refresh time went from almost 2 minutes to 25 secs.
I am guessing that this setting is set by the OCMT oracle client tool installation and not the gateway? No idea, but anyway it needs to be changed...