Problem with ITS memory configuration

HI,

when the user is trying to exceute huge reports from the portal ,he is getting error like "Runtime error:Assignment to Context failed(context overflow)!"

As suggested by SAP note :853489 there needs to be change in the parameter MaxCtxtsize .Current MaxCtxtsize value is: 5242880KB(5GB). when I asked some of my colleques they suggested to increase th value to 7864320(7.5GB).But as per the note its mentioned that sixe should not be more than 2GB.Can any one tell me what should be the Maxctxt value inorder to solve this problem.and also how to restart the ITS server after changing the parameter value.Is it Auto restart link which is visible in the ITS?

Pls its very urjent.....! Thanks in Advance

Regards,

Krishna