Why is this an issue?

To simplify large project management, review and evolutions, there should not be more that one architecture declaration per file.

How to fix it

Code examples

Noncompliant code example

File1.vhd:
architecture a1 of e1 is
begin
end;

architecture a2 of e2 is
begin
end;

Compliant solution

File1.vhd:
architecture a1 of e1 is
begin
end;

File2.vhd:
architecture a2 of e2 is
begin
end;