MUTEXes in PLSQL?

I am writing a trigger to calculate the value of a column in a row in a another table in processing the current trigger for a different table. I need to make sure that the row in the other table is not updated by other processes while I am processing this trigger.

How may I do that?

Also can you run a "select count(*) where .." on the current table you are processing in the trigger without getting "mutating.. type errors."

I am using 10G.

I need to check the inventory of the item before I can let the order through but also I need to check current order table to see if there are  any unprocessed orders that pre-reserved the same items from the inventory.

So total available items in inventory will be Inventory Items - Unprocessed Order PreReserved Items.

If available items are not there to process current order I have to prevent it from going through. Meanwhile I cannot let anyone update the Inventory until I finish inserting the order with its pre-reserved items.

Thanks Received on Thu Feb 14 2008 - 16:29:00 CST