Some of my colleagues told me that session consumes lots of memory to the server.

What must I do to effectively used my sessions with minimal consumptions of memory in the server?

Can I pass the data from my sessions to a global variable so that it will not consumes lots of memory in the server?

ex.
after reading my session:

Code:
string username = (string)Session["username"];
if (username == null || username.Length == 0)
{
  Response.Redirect("~/Default.aspx");
}
can I do this so that my other pages can also redirect to the default page if the session["username"] has no value:

Code:
GlobalVariable.username = (string)Session["username"];
so that instead of using the above code, I am going to do this:

Code:
if (GlobalVariable.username == null)
{
  Response.Redirect("~/Default.aspx");
}
Thank you all!