RDF System Management Manual for J-series and H-series RVUs (RDF Update 13)

Receiver Process
A receiver process is a process pair that runs on the backup system. There is one receiver for each
configured extractor. A receiver process accepts audit records from its extractor, sorts them, and
then writes them to the appropriate RDF image trail, as shown in Figure 6. (The restartability of a
receiver ensures the receiver's correctness at process takeover or under any conditions requiring
resynchronization with its extractor.)
A receiver determines which updater will apply a given image record, and it sorts that record into
the image trail used by that updater. The records in the image trails are subsequently used by
updater processes to update the backup database.
Each receiver creates its own image trail files, preallocates extents, initiates rollovers, and manages
them, except for purging, a task performed by the purger process.
Image trail files are usually named as AAnnnnnn, where nnnnn is the number value in the range
000001 to 999999. During RDF initialization, special files are created, which are termed as BB
files. BB files contain transaction lists that are required for RDF takeover or Stop Update to Timestamp
operations, to undo the uncommitted work. Similar to AA files, BB files also have the nomenclature
BBnnnnnn, where nnnnnn is the number value in the range 000001 to 999999. If the number
of transactions in the system increases, then BB files size also increases, however not at the same
rate as AA files. The default extent size for BB files is 2400, 2400 and cannot be configured by
the user.
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. BB files are
created in the same sub volume as 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.
RDF Operations 35