RDF/IMP and IMPX System Management Manual (RDF 1.4+)

Introducing RDF
HP NonStop RDF/IMP and IMPX System Management Manual—524388-001
1-22
Updater Processes
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, RDF 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.
•
The monitor detects the unexpected termination of any RDF process and sends
out abort RDF messages.
•
You perform a NonStop SQL DDL operation on the primary system that includes
the WITH SHARED ACCESS option (for information about this, see Performing
Shared Access DDL Operations.
•
A takeover operation completes on the RDF backup system.
Audited Database Files
All database files on the backup system are audited files.
Each updater maintains a file status table to keep track of the files it has open. An
updater closes any database file that has not been updated recently. Updaters also
close database files when a STOP RDF or STOP UPDATE command is issued, or
when the updater restarts because of error conditions.
An updater process can have up to 500 files open simultaneously. When it has the
maximum number of files open and needs to open another file, it first determines if
there are any files that have not been accessed recently and closes just them; if all of
the open files have been accessed recently, then the updater closes all of them before
it can continue processing. For the SMF ramifications of this file limit see the note
under Using SMF With RDF in Section 2.