RDF System Management Manual

Introducing RDF
HP NonStop RDF System Management Manual—524388-003
1-21
RDFNET Process
With sorted image trails, the activity of any one image file typically remains so low that
it can be stored on the same disk volumes as the main database with no significant I/O
impact. This approach is not recommended, however, if you require very high RDF
performance or if RDF is running with the UPDATE option turned off; in this case, the
image trails could eventually fill the volume; in such cases, it is best to have volumes
exclusively dedicated to the image trails.
Image trails can be added only after RDF has been initialized but before it has been
started.
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 takevoer.
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
information associated with the data volume it protects (it ignores audit information
associated with volumes protected by other updaters). When it finds applicable audit
information, the updater sends the audit information 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.
Note. You should keep all image trail files off of the $SYSTEM volume and its controller.
Otherwise, if there is a lot of audit data to send from the primary system to the backup system,
it could take a while for the updaters to start.