RDF/IMP and IMPX System Management Manual (RDF 1.3+)

Introducing RDF
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
1-18
Updater Processes
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 an SQL DDL operation on the primary system that includes the WITH
SHARED ACCESS option (for information about this, see Performing Shared
Access DDL Operations.
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.
UNDO Pass
Updaters perform an UNDO pass over the image trail during the final phase of RDF
takeover and stop-update-to-timestamp operations. This is because data already applied
to the backup database must be undone if the associated transaction did not commit prior
to the start of the takeover operation or prior to the specified timestamp.
Restart Information
RDF has a CONTEXT file in which each updater process maintains a context record. A
context record specifies the position (referred to as the restart position) in the image trail
where the updater was at the last context save point. All data for the associated data
volume in the backup database prior to the specified restart position is safe on disk (has
been applied to the backup database).
If an updater detects a restartable error, it restarts. Upon being restarted, an updater reads
its context record and restarts processing in the image trail at the specified restart
position.