"Being stored" sounds like the data is stored there now, perhaps temporarily. If the data is usually stored there, we just say "The data is stored in memory."
Also, "memory" in the computer context is an uncountable noun, so it doesn't need the article "a".
I want to eat an orange. I eat a lot of oranges.
I want to drink orange juice. I drink a lot of orange juice.
My program stores the data to memory. It uses a lot of memory.
If you say "a memory", it's usually about one story you remember from the past.
I have a nice memory of my family visiting France.
This is different from talking about a person's memory in general (this sentences uses both meanings together):
The memory of my family in France is fading from my memory.