HP XP Continuous Access Software - Manual (Page 100)

100 Continuous Access XP for the XP1024/XP128
Switching operations to remote sites
If a disaster or failure occurs at the primary site, the first disaster recovery activity is to switch operations
to the secondary site. Continuous Access XP Synchronous S-VOLs are recovered individually based on the
pair status and P-VOL fence-level information for each pair. Continuous Access XP Async S-VOLs are
recovered based on pair status and consistency status (at the RCU).
Basic procedures for switching operations to the remote backup site are:
1. Analyze currency of Continuous Access XP Synchronous S-VOLs (see ” Analyzing currency of
Continuous Access XP Synchronous S-VOLs ” on page 100) and consistency of Continuous Access XP
Asynchronous S-VOLs (see ” Analyzing consistency of Continuous Access XP Asynchronous S-VOLs ” on
page 101).
2. Record consistency time (C/T) of each Continuous Access XP Async group. Suspended Continuous
Access XP Async S-VOLs with consistency status of group indicate the same C/T. Consistency status
and consistency time are displayed only at the RCU.
Remember that the Continuous Access XP Async time-stamp and C/T information indicates MCU
service processor time, not host system time.
3. Perform file recovery as needed (see ” File and database recovery procedures ” on page 99). Use the
C/T of each Continuous Access XP Async group to retrieve lost updates.
4. At the remote site, connect to each RCU, and delete all Continuous Access XP Synchronous pairs. For
Continuous Access XP Asynchronous pairs, delete all consistent pairs in a group at one time using the
pairsplit-S command with the C/T delete range option. This option prevents you from accidentally
using inconsistent pairs for disaster recovery.
CAUTION: After an S-VOL changes to simplex, you cannot distinguish it from a non-Continuous
Access XP simplex volume. The Continuous Access XP Async C/T is also discarded when the pair
is deleted.
5. If necessary, use the logical volume manager to change volume labels of S-VOLs.
6. Ensure that all required file recovery procedures are complete before varying S-VOLs online.
7. At this point, start critical applications at the remote site with previous S-VOLs taking the place of their
P-VOLs.
Analyzing currency of Continuous Access XP Synchronous S-VOLs
Table 20 shows how to determine currency of a Continuous Access XP Synchronous S-VOL based on its
pair status and P-VOL fence-level setting. For Continuous Access XP Sync pairs with a P-VOL fence-level
setting of Never, further analysis is required to determine currency of these S-VOLs. Determine currency of
these S-VOLs using the sense information transferred via the host failover, or by comparing the contents of
the S-VOL with other files confirmed to be current (such as database log files). These S-VOLs should be
recovered using files confirmed to be current.
NOTE: Actual data recovery must be done using recovery point data in the database redo log.
Table 20 Determining Continuous Access XP Synchronous S-VOL currency based on its pair status and
P-VOL fence-level setting
Status of S-VOL Fence level Currency of S-VOL
SMPL Data
Status
Never
Inconsistent. This S-VOL does not belong to a Continuous Access XP volume
pair.
Even if you established a
Continuous Access XP pair for this volume, you
must regard this volume as inconsistent.
COPY Data
Status
Never
Inconsistent. This S-VOL is not synchronized because not all cylinders have
been copied from the P-VOL yet. This S-VOL must be initialized (or copied
from the P-VOL at a later time).