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

Transactions that must be undone during this undo pass are stored in the ZFILUNDO file in the
Master Image Trail subvolume.
Phase Three Undo Pass
This is also known as Network Undo. If you are running in an RDF network and you lose one
or more primary systems, you must do a takeover on all backup systems in your RDF network.
For a complete description of the takeover operation in an RDF network, see “RDF Takeovers
Within a Network Environment ” (page 278).
Transactions that must be undone during this undo pass are stored in the ZNETUNDO file in
the Master Image Trail subvolume.
When the takeover operation completes, your backup database is in a consistent and stable state
with regard to transactions that committed on your primary system.
Preparing for Takeover Processing
Before you issue a TAKEOVER command from the backup system, you need to specify the name
of the control subvolume in the command that starts your RDFCOM session:
>RDFCOM control-subvol
Issuing the TAKEOVER Command
To request the takeover operation, enter the TAKEOVER command:
]TAKEOVER
If the communications lines are up and the monitor and extractor are still running on the primary
system when you issue the TAKEOVER command, RDF rejects this command.
If the communication lines are down or the monitor and extractor have failed when you issue
the TAKEOVER command, RDF executes the command on the backup system:
• If RDF is running with updating on, RDFCOM sends a takeover message to the receiver and
all updater processes.
• 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. (The name of this monitor on the backup system is generated by the system.)
• If RDF had been stopped, RDFCOM starts the monitor in TAKEOVER mode. The monitor
starts a receiver process and all updater processes. (The name of this monitor is generated
by the system.)
If a monitor process was started on the backup system, the monitor stops after the other RDF
processes are shut down.
The following example shows how to use the TAKEOVER command when RDF is running with
updating enabled. The command sequence in the example causes the backup system \TORONTO
to take over processing from the primary system \SANFRAN.
1. At the TACL prompt on the backup system (\TORONTO), start an RDFCOM session and
specify the control subvolume name:
>RDFCOM SANFRAN
2. At the RDFCOM prompt, issue the TAKEOVER command:
]TAKEOVER
RDF displays the following prompt message:
*** TAKEOVER assumes a disaster on \SANFRAN has occurred.
Are you sure you want to TAKEOVER?
136 Managing RDF