HP NonStop RDF, Management Manual

Page: 45 / 478

Sorted Image Trails
RDF maintains its image data on disk volumes specified during RDF configuration. On each of
these volumes, the collection of files that contains image data is known as an image trail; that
is, there is one image trail per individual image trail volume.
The standard image trail used by RDF, called the master image trail, contains the transaction
status records that hold key information about whether a transaction has committed or aborted.
The master image trail is stored on the disk volume specified by the master receiver’s
RDFVOLUME configuration option. You cannot configure any updaters to the master image
trail.
Secondary image trails primarily contain the audit records that log changes made to the user's
database on the primary system. Updaters read secondary image trails and apply the changes
recorded in the records to the database on the backup system. All updaters must be configured
to secondary image trails. You can configure up to 255 secondary image trails. Each secondary
image trail is stored on a separate volume, specified by the IMAGETRAIL configuration option.
RDF uses multiple sorted image trails. With this feature, the receiver detects which updaters are
associated with which image trails. When it receives a record, the receiver identifies the updater
that will apply the record to the backup database. The receiver then sorts the record into the
image trail used by the updater responsible for applying the record.
Figure 1-6 Receiver Process Operation
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