You will see a property called “Long List” against picklists. Although it is often flagged as TRUE for dynamic picklists, there are seldom used against static LOVs.
Siebel recommends that any picklist having more than 500 values must have the Long List property set to TRUE. This is equally applicable to static or dynamic picklists.
Typically, when you select a value that has to pick list, Siebel automatically queries the picklist BC to determine the position of the current value against the valid list of values. This results in an improved user experience since the user can choose to select other values in the neighbourhood of the original value.
When set to true, Long List will prevent Siebel from firing blank query set the database to find a position in the picklist. This will result in improved performance when working with the drop-down values.
If you are facing performance issues with pick lists it is worth checking out whether the problem goes away by setting Long List to TRUE.