RDF System Management Manual for H-Series RVUs (RDF 1.8)

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 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.
• 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:
CREATE PURGE (if REPLICATEPURGE is enabled) PURGEDATA ALTER MAXEXTENTS
(used only for increasing MAXEXTENTS)
• For NonStop SQL/MP and NonStop SQL/MX files only, performs the following DDL
operation: PURGEDATA
An updater cannot always respond immediately to the STOP UPDATE and STOP RDF commands.
If an updater has audit information queued for the disk process, the updater must wait until all
of that information is processed before it can shut down.
You specify the primary and backup CPUs for each updater. If the original backup process has
to take over because the primary CPU failed, this backup process runs by itself. When it determines
that the primary CPU has come back up, it creates a new backup process in that CPU.
When it has to take over, the original backup process becomes the primary process, and remains
so even after it creates a new backup process; that is, the updater does not switch back to the
original CPU configuration after the new backup process is created. If you stop the updaters by
way of a STOP RDF or STOP UPDATE command, however, when you restart the updaters, your
original configuration is once again used.
The updaters will shut down if any of the following occurs:
• You issue a STOP RDF, STOP TMF, or STOP UPDATE command on the primary system.
• You issue a STOP RDF command on the backup system when the communications lines
between the two systems are down.
52 Introducing RDF