I was having a good thought on how to minimise downtime on a migration project I'm currently working on (informix to oracle with 7TB of data).
Obviously you can't do anything with log shipping, etc. Then I had a brainwave. Why not ship deltas at the application level using TDMS?
Now I'm not a TDMS expert and don't know what limitations there are but my thoughts were as follows.
Copy Prod to Temporary hardware (system down so no new data is created) - Date and time stamp Noted
Start Prod back up
Export/import temporary system to new DB
Then using TDMS extract all data from the above date and time stamp (trickle feed).
Then at a convienent point. Stop the production system use (i.e. lock all users, finish all batch jobs) and extract the final delta via TDMS.
Start New Prod!
This is something I'm quite willing to research and do a proof of concept with if there arn't any major hurdles.
Any comments would be greatly appriciated