Chapter 22. Replication and DR deployment with backup applications 389
If the Last sync time flag on all the cartridges indicates a time later than the backup complete
time, your backup image was fully replicated.
There could be a time difference between the source backup server and the source
ProtecTIER server. Your administrator should be aware of the discrepancy, measure it
regularly, and communicate the delta to your DR administrator or operators.
For example, if the backup server is two hours behind, a cartridge may have a sync time that
precedes its backup complete time. If there is uncertainty regarding the time differences,
compare the nominal size of the cartridge to the catalog or database value as an additional
(not a substitute) layer of verification.
22.4 Replication best practices for OST
In this section, we describe the OST NetBackup application programming interface (API)
capabilities. We also describe the typical considerations and best practices for a replication in
an OST configuration.
The OST interface is a NetBackup API supporting communications between NetBackup
systems and OST-enabled ProtecTIER systems. The OST interface provides the following
capabilities:
򐂰 The NetBackup software directs ProtecTIER systems regarding when to create, copy,
delete, or restore backup images.
򐂰 Backup images can be replicated to up to 12 different ProtecTIER systems.
򐂰 Workloads and performance are balanced between NetBackup media servers and
ProtecTIER systems.
򐂰 Detailed statistics about the state of the ProtecTIER systems are available through
the API.
With OST, a ProtecTIER server can be integrated with NetBackup to provide backup-to-disk
without needing to emulate tape. ProtecTIER uses a plug-in that is installed on an
OST-enabled media server. With this plug-in, a ProtecTIER server can implement a
communication protocol that supports data transfer and control between the backup server
and the ProtecTIER server.
Attention: When processing the cartridge list to find a complete set of DR tapes, you must
track the date and time discrepancies. Compare the date and time values of the source
master backup server and the source ProtecTIER system. The destination environment
might be in a different time zone or might be set to the incorrect date and time.
Use the
source date and time, rather than the destination sync time, when comparing
cartridge states to the backup catalog or database. The destination sync time should be
used only to determine which cartridges are complete.

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