Oracle 9 / 10 compatibility

I have a tricky problem relating to Oracle and need some ideas... I have a standard business application (V5.1) that is compatible up to Oracle 9.2. Actually it is running on Oracle 9. Now support for Oracle 9 is discontinued. This means that upgrade to Oracle 10 is required. The business application (V5.1) does not support Oracle 10. Now we need to upgrade the Application to V7.0. The problem is, the upgrade procedure is as described below: On friday evening: Productive business application V5.1 with Oracle 9 (V5.1 does not support ORA 10) Upgrade starts with upgrading the business application to V7.0 (only ORA Client 10 is supported), but we still have Oracle 9 so upgrade procedure fails (but V5.1 does not support ORA 10). What can we do? Migrating data from ORA9 database to ORA 10 database? How would this be done, is this complex? Or can we install ORA 10 Client with Oracle 9 database to perform the upgrade?