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

Introducing RDF
HP NonStop RDF/IMP and IMPX System Management Manual—524388-001
1-21
Updater Processes
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, an 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 files only, performs the following DDL operation: PURGEDATA
An RDF updater can send up to 28 KB of audit information to the disk process in a
single request and can manage two outstanding requests at any given time. The
updater is a multithreaded process. The two most prominent threads perform these
tasks:
•
Reading and queueing audit for submittal to the disk process
•
Submitting the audit to the disk process and handling replies from that process