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

Image trails can be added only after RDF has been initialized but before it has been started.
RDF Control Points
When the extractor has no information to send from the audit trail, it transmits a buffer containing
no audit images (an empty buffer) to the receiver. When the receiver process receives an empty
buffer, it generates an RDF control-point record in each image trail. Therefore, even when no TMF
transactions are generated on the primary system, RDF adds internal control points to the image
trail on the backup system. The file-filling rate for RDF control point records is very slow.
A receiver determines which updater will apply each audit record, and sorts the data 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 .
The receiver also adds RDF control points to individual image trails if they have not received new
audit while other trails have. Thus, the image trails can appear to be growing in size even though
no transaction activity is taking place on the primary system. The primary importance of RDF Control
Points is that they are used to reflect accurate RTD times for the updaters when new audit has not
been added to their image trails for any period of time. They are also useful for the coordination
of other special operations.
RDFNET Process
The RDFNET process is a process pair that runs only on the primary node of the network master
in an RDF network. The RDFNET process creates synchronization information used only during RDF
takeover.
Updater Processes
An updater process is a process pair that runs on the backup system when updating is enabled or
during takeover processing. Every volume on the primary system that is protected by RDF has its
own updater process on the backup system.
Each updater reads the image trail to which it has been configured, looking for audit records
(image records) associated with the data volume it protects (it ignores audit records associated
with volumes protected by other updaters). When it finds applicable audit records, the updater
sends the audit records to the disk process to be applied to the backup database.
Each updater performs the following functions:
• Reads large blocks of data from the RDF image file and searches for image records associated
with the updater’s volume on the primary system.
• Opens and closes database files on the backup system for updating and maintaining the
backup database.
• Defines restart points and updates restart information in the context file (named CONTEXT).
For an explanation of restart points, see “Restart Information”.
• Sends information to RDFCOM for use in the STATUS RDF command display.
• Issues a logical REDO request to the disk process (during the normal forward pass over the
image trail) for each update associated with its volume.
• Issues logical UNDO requests to the disk process when backing out changes associated with
transactions that need to be undone during RDF takeover or stop-update-to-timestamp operations.
• Bundles the REDO and UNDO requests into batch TMF transactions, the duration of which is
specified by the UPDATERTXTIME configuration parameter.
• For Enscribe files only, performs the following DDL operations:
RDF Operations 37