Availability Guide for Application Design

Data Protection and Recovery
Availability Guide for Application Design—525637-004
4-31
Solution Using a Database Snapshot
within the lag time period. For example, if the lag time is 7 minutes and the snapshot is
taken 2:07 a.m., you can peruse an accurate snapshot of the database at 2:00 a.m.
Performing Remote Duplicate Transactions
By writing your own application to perform remote duplicate transactions, you can
obtain an accurate snapshot of the database without any interruption to online
operations. Writing such an application, however, is not an easy task.
When you want to take your snapshot, you must stop sending transactions to the
backup database until the batch process has finished. Meanwhile, you can send all
transactions destined for the backup to a queue file, which can be used to synchronize
the databases after the batch application has finished.
You can use either the transaction playback or the trickle catchup approach for
queuing and dequeuing transactions. Refer to Queue Files on page 4-19 for details on
these techniques. If the order in which transactions are performed is important, then
you should use trickle catchup. Otherwise, transaction playback is simpler to
implement.