Distribution of temp db in multiple files

Question

HI All,

 

I recently got one task for distribution of tempdb load to multiple ndf files. I found some tips  like based on number of processor we can make ndf files.

My question is

 

--Does it require any down time for a higly used OLTP database, just by simply writing alter command for adding a file group.

--How can i make sure traffics are distributed equally to all files (.mdf and .ndf)

--Any new suggestions.

 

 Thanks,

Manish