RDF/IMP and IMPX System Management Manual (RDF 1.4+)

Introducing RDF
HP NonStop RDF/IMP and IMPX System Management Manual—524388-001
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Updater Processes
UNDO Pass
Updaters perform an UNDO pass over the image trail during final processing of RDF
takeover and stop-update-to-time operations. This is because data already applied to
the backup database must be undone if the associated transaction(s) did not commit
prior to the start of the takeover operation or prior to the specified timestamp.
For takeover operations there are three phases of undo: local undo, file undo (if file-
incompletes from the primary system are still unresolved), and network undo (if you are
operating in an RDF network). For stop-update-to-time operations there is only local
undo (file-incompletes cause abend, and network undo is not supported).
Restart Information
RDF has a CONTEXT file in which each updater process maintains a context record. A
context record specifies the position (referred to as the restart position) in the image
trail where the updater was at the last context save point. All data for the associated
data volume in the backup database prior to the specified restart position is safe on
disk (has been applied to the backup database).
If an updater detects a restartable error, it restarts. Upon being restarted, an updater
reads its context record and restarts processing in the image trail at the specified
restart position.
Partitioned Files, Alternate Key Files, and Indexes
Each updater is responsible for applying audit data to partitions corresponding to the
volume on the primary system that updater is protecting. Updates are applied directly
to the specific partition, regardless of whether it is a primary or secondary partition.
RDF does not use the file system for partition mapping.
Furthermore, because updates to the backup database are applied by logical
REDO/UNDO operations, alternate key files and NonStop SQL indexes are not
affected by an update to a file or table. Alternate key files or NonStop SQL indexes are
updated independently as a consequence of the individual audit records generated on
the primary system by TMF software.
File System Errors Involving Data Files
File system errors can occur when:
•
A file is created.
•
A file is opened.
Note. You must be sure that volumes on the primary system containing alternate key files and
indexes are protected by RDF. It is not sufficient to protect just the associated data file or table
(particularly in the case of alternate keys). Likewise, if primary partitions reside on volumes
protected by RDF, you must ensure that the secondary partitions are also configured for
protection.