Question about dataspace

I cannot understand dataspace very well. I have some questions about it. Each time I want to alloc a piece of memory, I must create a dataspace first? I look at the example code of memory allocation. I found after create adataspace, we call L4Re::Env::env<http://l4re.org/doc/classL4Re_1_1Env.html#aa1181d6256037deda5b5f83c2006ba60>()->mem_alloc()->alloc() to alloca memory via dataspace. Can I call this function multiple times on the same dataspace instance without free? If so, what is its effect? In addtion we use attach to map the dataspace. Can I attach the same dataspace multiple times without free? In this case, does it mean that the same physical memory is mapped into different virtual address?