Frequency and retention for backup copies

When developing a backup strategy for your databases you need to consider how frequently to make new copies and how long to keep old, back-level copies.

There are no precise answers to these questions. Generally, the more frequently you copy, the less time recovery takes. The farther back in time your old copies go, the farther back in time you can recover; remember that program logic errors are sometimes not discovered for weeks. However, making each new copy requires work, and each old copy you save uses additional resources.

The only firm guidelines are these:

• If you do an initial load of a database, immediately make a backup copy of it.
• If a database is composed of several data sets, be sure to copy all data sets at the same time.
• If you reorganize a database, immediately make a new backup copy of it.

  Exception:  It is not necessary to make backup copies after DEDB online reorganizations.

You can reduce the amount of work required to create non-concurrent image copies by taking the image copies while databases are quiesced instead of while databases are offline. Quiescing a database leaves the database online, allocated, and authorized with DBRC. Application programs are placed in a wait state. Because quiescing databases requires less work, it is possible that you can increase the frequency with which you create image copies.

If you take databases offline to create non-concurrent image copies, the databases are taken offline, deallocated, and unauthorized with DBRC. Application programs encounter an unavailable database.