Halachos for Erev Shabbos Kodesh

1) When a new oven is purchased, it is extremely praiseworthy to dedicate the oven to one food class, and have a separate oven or heating element for the opposite food class.

Indeed, many people purchase ovens with 2 separate compartments (Double Decker oven) and dedicate one to meat and one to dairy, and this practice is commendable as it prevents many Kashrus problems that often arise when having only one oven .

2) When using a Double Decker oven, it is best to dedicate the top oven for meat and the bottom one for dairy, as meat foods  tends to release more steam (due the fats  in meat) than dairy foods, and of course heat rises. (See Sefer HaKashrus page 42)

Although when a Double Decker oven is used it is permissible for both of the ovens to be in use at one time with opposite food items, some people are scrupulous to not have them both cooking at the same time. (See Sefer Kashrus  V'Shabbos B'Mitbach page 160 and Kovetz M'Beis Leivi Vol. 3 page 21 for more details about this)

Halachos for Shabbos Kodesh

1) Disposable aluminum pans that are used for baking and cooking, which are manufactured outside of the United States of America, according to some Kashrus researchers , may have a Kashrus problem due to the possibility that animal fats are used in the manufacturing process.

The problematic pans, may be eliminated by  cleaning them  thoroughly with soap and water and then used.  (Psak of Maran Rav Yosef Shalom Elyashiv Shlita quoted in Sefer HaKashrus page 43 footnote 68)

It is for this reason that pans with Hechsherim (rabbinical certification) are available on the market.

2) The pans manufactured in the United States, apparently do not utilize such a process, and may be used without a Hechsher.

In any case, a Rav should be consulted for Halacha L'ma'aseh.

Regarding if these "disposable" pans require Tevilah, we shall discuss this at length in the future B'Ezras Hashem.