Availability Guide for Application Design

Data Protection and Recovery
Availability Guide for Application Design—525637-004
4-30
Solution Using a Database Snapshot
application. Using RDF, however, you have a tradeoff between having a completely
accurate snapshot and taking the snapshot instantaneously. If you want the snapshot
to be completely accurate, with no partially committed transactions, you can do so by
tolerating a brief outage on the primary system while the databases are synchronized.
You can avoid this brief outage if you can tolerate partially committed transactions in
the snapshot or you can extract your snapshot from the backup volume in such a way
that it does not contain partially committed transactions.
You can create a snapshot without partially committed transactions and without an
outage by designing your database to include a timestamp field in each record. After
taking your database snapshot by stopping the update, you can use the RDFCOM
utility to determine the amount of time that the backup volume lags the primary volume.
You can then peruse the snapshot, excluding records that have been timestamped
Figure 4-10. Batch Processing With and Without Batch Windows
Online
Online
Online and Batch
Database
Snapshot Snapshot
Online Online
Batch
Database
Tape
Backup
Online
Dump
With Batch
Windows:
Without Batch
Windows:
Time in Online Processing
Time in Batch Processing
Data Flow
VST310.vdd