time control question?

Is the time control 30/90 SD/60 The same as 30/90 G/60????

No.  SD 60 means Sudden Death in 60 minutes; each player uses the same 60 minutes and whoever exceeds 60 minutes loses the game.  G 60 means Game in 60 minutes; each player has 60 minutes apiece, so the game could reach two hours.  In which case, I would think the proper terminology should be Game 120 minutes.

This indicates that the two designations are the same.

http://monroi.com/chess-blog/chess-experts/chris-bird-blog/119-chris-bird-blog/899-chess-clocks-understanding-time.html

"As you can see, sometimes people quote hours or minutes and sometimes people use “SD” or “G” to define a time control that means “the rest of the game” or “to the finish.” There are items in brackets and sometimes things are spelled out. There is no consistency although chess players continuously have to determine what these things mean. "

Time cannot be shared. Each player has their own 60 minutes.

Yes, that is correct; time is not shared.  Sorry.

thank you