HP Application Recovery Manager software A.06.10 Concepts guide (March 2008)

The first can cause major disruption to the application’s operation. The second can
produce many large transaction log files, putting extra load on the application system.
Zero downtime backup (ZDB) uses disk array technology to minimize the disruption.
In very general terms, a copy or replica of the data is created or maintained on a
disk array. This is very fast and has little impact on the application’s performance.
The replica itself forms the backup, or it can be optionally streamed to tape using
third–party software without further interruption to the application’s use of the source
database.
Depending on the hardware and software with which it is created, a replica may be
an exact duplicate (mirror, snapclone), or a virtual copy (snapshot) of the data being
backed up.
In ZDB, replication (the process of creating or maintaining a replica) is the critical
factor in minimizing interruption to the application.
Figure 2 Zero downtime backup and instant recovery concept
Online and offline creation of replicas
For database applications, backup can be performed with the database online or
offline:
• Online backup
The database is placed in hot-backup mode while a replica of sections to be
backed up is created. In this mode, any changes to the database are written to
transaction logs, not the database itself. When the database is fully functional
again, it is updated from the transaction logs. This allows the database to be
operated on without stopping the application.
• Offline backup
Database operation is simply stopped while a replica is created. No transactions
are possible during this time.
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