RDF System Management Manual

Entering RDFCOM Commands
HP NonStop RDF System Management Manual—524388-003
8-109
Command Overview
Usage Guidelines
The TAKEOVER command is customarily issued when the primary system fails or
otherwise becomes unavailable, and makes the backup database the primary
database.
For takeover considerations in a ZLT environment, see Section 16, Zero Lost
Transactions (ZLT).
When you issue a TAKEOVER command without the exclamation point, RDF
determines whether the monitor and master extractor processes are running on the
primary system:
•
If the communications lines are operational and both the monitor and master
extractor processes are still running, the TAKEOVER command fails.
•
If the communications lines are down, RDF proceeds as if either the monitor or
master extractor process is not running and executes the TAKEOVER command.
If RDF is running with updating on, RDFCOM sends a takeover message to each RDF
process.
If RDF is running with updating off, RDFCOM stops the receiver process and starts the
monitor in takeover mode. The monitor then starts a receiver process and all updater
processes.
In a non-network configuration, a takeover operation occurs in two phases.
•
Phase 1 (local undo) undoes transaction data that was incomplete at the backup
system at the time the primary system failed.
•
Phase 2 (file undo) only runs if volumes went down on the primary system,
transactions were aborted, and the volumes were never reenabled on the primary
system before the primary system was lost. In that situation, RDF determines what
Backout could not undo, and runs the undo.
A network configuration adds a third phase (network undo). Refer to Section 13,
Network Transactions.
Caution. The TAKEOVER command is not a normal operational command. Operators
should never issue this command strictly on their own initiative. Issue this command
only when specifically told to do so by someone in high authority.
It is important to ensure that the RDFCOM session uses the appropriate RDF control
subvolume which is associated with the primary system for this TAKEOVER operation. To do
this, specify the RDF control subvolume through the OPEN command or on the RDFCOM
command line.
Before initiating a takeover, restore all image files to their original location in the image trail (if
you moved them). If you do not restore the image files the takeover may fail or appear to
complete successfully but leave the backup database in an inconsistent state.