Hi Reza,
When you change the virtual memory , be carefull, you can make it thrice or twice , but remember select the drive in which sap application is installed and drive should have enough space.
When you change the virtual memory , it will ask for restart of the server.
So before doing , you need to assigned the virtual memory after taking a proper decision regarding how much you need to increase.
Please update me.
With Regards
Ashutosh Chaturvedi