Complete divine in additional Domains says that when a creature that casts arcane spells gains a domain, then
If he is a spellcaster who has a spell book as a wizard does, then he must find or buy a roll of that spell and pay the usual price to write the spell in his spell book. In cases where the spell is only divine, the magician can write a divine scroll in his book. The wizard can then memorize a domain spell of each level each day. (twenty)
(Readers, try not to look at the pre-Third edition finished memorize; assume Complete divine medium prepare.) While Complete divine provides examples of how an additional domain affects the launching ability of, respectively, a paladin, a cleric and then a sorcerer; it does not provide an example of how an additional domain affects the conversion of a wizard.
It is this One domain of each level every day. in addition to the normal spell assignment of the wizard, therefore, essentially, an extra spell slot per day in each spell level above 0, but that is only capable of maintaining a spell domain, or that phrase limits the Spell preparation options of the wizard, but leave the wizard's spell slots unchanged? Or is there another completely different way to read this that I'm overlooking?
An example: Travaran is a human diviner 7 / divine oracle 6. A class feature of level 1 of the divine oracle of prestige class (CD 34-6) gives you access to the Oracle domain (Compendium of Spells 277-8) that has the first level domain spell the level 1 spell normally Sor / Wiz identify [div] (Player's manual 243).
Until he won that first level of the prestige class divine oracle, Travaran, who already had the spell identify in his spellbook, he could prepare and launch as many times as he wanted. identify spell (within the limits of their spell slots and casting ability, of course). However, after taking that level of divine oracle and gaining access to the Oracle domain, you can now, for example, prepare a identify Do you spell on each of your spell levels from 1 to 7? Or can you now, for example, prepare the identify only spell once in each of your spell levels from 1 to 7? Or, you know, something else?