low virtual memory!

Hi experts,

Ram size : 16 GB

1.we are receivning alerts Virtual meory  using more than  90%..

2.how to find weather  virtual memory full or not ?

3.when Ram size 16 Gb , how much Virtual memory size?

4.I ran thi is query "SELECT * FROM sys.dm_os_ring_buffers " but i did not understand  can you sugest me!

5. what is the solution?

Thanks in Advance.

Vijay