Freezing Inventory Org temporarily for Physical Inventory

Hi Team

I have a business requirement here.\

Physical inventory takes place one a year in the organisation. We have 5 diffrent inv orgs.

Generally it takes 3 to4 days to complete the physical inv process.

How can i freeze  (restrict user from creating INternal Req ) for the particular inv org for time being . Lets say for 3 days. And again opeing that inv org again for transaction.

Because oracle does not restrict in transaction once the snap shot are taken.

thanks

pankaj