Minimizing your Script
Gamemode Scripts
Avoid using gamemode scripts wherever possible. Use quest scripts if you can, or try to find ways to put as much of the script work into OnLoad, OnEquip, and ScriptEffectStart blocks as possible.
If you need to use a GameMode block, use an 'if' test or a flag so the code will only run when necessary. For instance, if you need to run an item script whenever the player hits a switch, place this on the switch:
scn YourSwitchScript short Working begin onActivate set Working to 1 end
and this on the item:
scn YourItemScript begin GameMode if YourSwitchScript.Working ... endif end
An important note on If blocks vs early Returns
The Morrowind scripting community determined that the script engine would process all code inside of an If block (even if the condition was false) until the script engine could find an exit point. An exit point can be either an accessible RETURN call, or the end of the script. It appears that this is also true in Oblivion - see the OblivionScriptsOptimized thread linked below.
This:
;; unoptimized begin GameMode if (some condition) (some extremely long code block) endif end
Is considerably more expensive than this:
;; optimized begin GameMode if (some condition) == 0 ;; logical negation RETURN endif (some extremely long code block) end
You can also do this:
;; optimized 2 begin GameMode if (some condition) if (some condition) == 0 return endif (some extremely long code block) endif end
In short, best practices for Oblivion scripting are to call RETURN early and often. For large scripts this subtle coding difference can yield dramatic performance gains.