2 room reservation split in 2?
 

I had a reservation for 2 rooms this weekend, now when I log in I see 2 identical reservations, the only difference is new res. number for the second one, plus it can't be opened (redirects to error page, "our res. system is down").

When I view the first, original one, it shows only 1 room.

Is it a common practice for Marriott split the reservation in such a way?

MARSHA handles things two ways.

1) You may have two rooms on a single reservation.

2) You may have a "split" reservation, where each room is on its own separate reservation, and the two reservations point back at each other.

No, I do not know why it is one way or the other on different occasions.

It is - that's how most hotels actually work. Each confirmation number reflects a single room whereas they may have given you 1 confirmation number (that was the first room), the rest of the confirmation numbers are related to that first confirmation number. To verify this, give the toll-free a call (although you should be able to see it on the internet) & confirm your reservations.