RDF/IMP, IMPX, and ZLT System Management Manual

Managing RDF
HP NonStop RDF/IMP, IMPX, and ZLT System Management Manual—524388-002
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Backing Up Image Trail Files
system \A keeping half of the table on system \A and moving the other half to a table
on system \X because RDF on system \X does not know about the shared access
NonStop SQL/MP DDL operation (the Stop-RDF-Updater audit records for the
operation on system /A go to system /B, not to system /Y).
Network Configurations and Shared Access NonStop
SQL/MP DDL Operations
Under certain circumstances, takeover network undo processing after having
performed a shared access NonStop SQL/MP DDL operation can lead to an abort with
database corruption.
You can, however, avoid that situation entirely by using the protocol described under
Network Configurations and Shared Access NonStop SQL/MP DDL Operations in
section 13 when performing shared access NonStop SQL/MP DDL operations in a
network environment:
Backing Up Image Trail Files
The RDF image trail files exist strictly for use by the receiver, purger, and updater
processes, and should not be explicitly opened by RDF users for any reason, including
backup to tape. Once the receiver has processed an image file, this file may no longer
serve a purpose (except in the case of triple contingency, where the file may be used
in a COPYAUDIT operation). In particular, image files are not like TMF audit dump
files; they cannot be used to restart RDF in the same way that audit files are used to
restart TMF. Typically, image files should only be accessed by RDF itself or by RDF
specialists and support people.
However, if you do wish to back up image trail files at your site, you should be aware of
the way RDF accesses these files and the ramifications of this access. When the
receiver updates an image trail file, it opens that file with shared read/write access.
When updaters read audit information from an image trail file and apply it to the backup
database, they open the image trail file with shared read-only access. When the RDF
purger process determines that a particular image trail file is no longer needed by any
updater, it purges that file unless the current RETAINCOUNT precludes doing so. If
you want to back up an image trail file, you should hold that file open to prevent the
purger from purging it until your backup is complete.
For a successful backup, follow these steps:
1. Execute a process that opens the image trail file with shared read access. This can
be a simple process that you supply to perform only this operation. When the
purger determines that all updaters are finished with this image trail file (named,
say, AA000007), and have moved on to the next image trail file (named, say,
AA000008), then it may try to purge AA000007. The purge operation will fail,
however, because your process still has AA000007 open. The purger will terminate
the purge attempt and try it again later. As long as your process keeps AA000007
open, the purger cannot purge it.