RDF/IMP and IMPX System Management Manual (RDF 1.3+)

Managing RDF
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
5-26
Backing Up Image Trail Files
3. If you are doing a move boundary operation, run FUP Reload on the backup system.
4. Issue a START UPDATE command on the primary system.
Whether or not RDF aborted while the updaters were shutting down, if one or more
updaters did not generate a message 733, issue a START RDF, UPDATE ON
command (only those updaters that did not generate a message 733 are started). Check
the RDF log again to see whether all of the updaters generated a message 733. If one or
more did not, issue another START RDF, UPDATE ON command, and so forth. When
all of the updaters have finally generated a message 733, then do the Steps 2 through 6
listed above.
Backing Up Image Trail Files
The RDF image trail files exist strictly for use by the receiver 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), the 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.
2. When the purger tries to purge AA000007 and fails, it writes a message denoting
this error to the EMS event log. This message implies that all updaters have moved
from AA000007 to AA000008 (or beyond), and will never need AA000007 again; it
is your only way to know for certain that AA000007 will never be needed again.
When this message is written, you can start the backup process to dump AA000007
to tape.