Fixed in 9.3.1 SP1 & 10.0 SP1 - If unable to upgrade please follow KB38019.
対処法
Development has built into the ArcSDE that the spatial index on ST_Geometry feature classes is used AT ALL QUERIES from 9.3.1 SP2 and 10 SP1 forward. If your customer cannot move to 9.3.1 SP2 or 10.0 SP1 then they will need to follow the steps in the KB38019.HowTo: Disassociate the st_domain_operators from the st_domain_stats type in Oraclehttp://resources.arcgis.com/content/kbase?fa=articleShow&d=38019If your customer follows the instructions in KB article, then the spatial index will be used when zoomed in (and performance should/better be acceptable or something else is impacting performance).