In our co the std cost is not updated till now.for eg the std cost of diesel is showing as 44 while it is more than 60 now.pl tell me as to which session to use to update the std cost of all the items in item data.

Hello UBhat:
If you update the cost price of item, it would have repercussions in finance module as entries (related to sales / production / purchase) to finance are passed based on cost prices of the items.
So before changing the prices, you have to discuss the matter with Finance department. For updating the prices of single item, you can go to the special menu of item data session and update the cost price of that item.
For changing the cost prices multiple items in one go, you can use update cost prices of the items session, which is available in cost price module.

There are few setting that needs to be checked before you update in item master- E.g. what it should be updated from. So check the cost price paarameters. You can do calculation and update under cost accounting menu. Cost price can be updated only against costprice calculation code maintained in cost price parameter. If you don't have a Bill of material then it is easy to asses the impact, but if you have a Bill of material then I will suggest you to run cost price calculation (no update) and check how it is going to impact (only if accounting wants to do this).

Arvind Patil