Integration

Hi,

What can be the possible options to maintain sequencing in Oracle SOA?
Ellboration:
Two type of messages are to be passed through the MW
1. Order
2. Order Approval

Order Approval can only go through to the target system if Order has been successfully passed through, where should this information be stored and checked upon everytime an Order Approval comes along?

In the DB where all the Order Ids should be recorded? against which Order approval would be first checked, if the Order id already exists in the DB? what other options are there?

And which is the most suitable?