"Manual" Mirror?

Can anyone offer some ideas on the following. I will have two servers A and B. A is online committing transactions. B is offline. At some point, a full backup of A's db will be effected to be duplicated into B. This is done, probably, with a tape. B is then relocated to a remote site (up to 50km away). B is then started up. Before B can get online the "new" transactions in A (after the backup to B) must be transferred to B. B is linked to A via a unreliable wireless link. My current thinking. To detect the changes after the backup. Extract this into ascii, compressed and emailed to B for further restoration. While this is going on, A is still effecting changes. At some designated time, B will take over from A but it is forseeable that in the background some changes at A are still being pumped to B. But this is minimal and should not severely impact B going online. Without incurring overheads of logging the transations in my application, is there some log file/table kept by Informix that will allow me to implement the above. Or is there some really simple method, I've overlooked. Any inputs will be welcomed.