
Determine Migration Approach
28
Determine Migration Approach
The best migration strategy for you depends on such factors as the cost of the
effort, the type of business you do, the size of your databases, and available
resources.
The following table highlights the advantages and disadvantages of each
migration approach:
For more information on these approaches, see the following sections:
• Parallel With Replication
• Cutover Without Replication
Approach Advantages Disadvantages When used
Parallel With
Replication
Easy fallback to earlier
release. You do not need to
rebuild previous release
databases.
Minimal system down time.
Can be complex in OLTP
environments.
Replication Server must be
set up, requiring extra
hardware and software.
This approach is best for
large 7x24 production
databases, maintaining high
availability, when:
• Rebuilding a release
database can take too long.
• The system may have a
large number of
transactions and complex
Transact-SQL queries
with subqueries.
Cutover
Without
Replication
Can be executed with
minimal resource demands.
Highest risk. Requires down
time for critical migration
tasks.
Recovery can be time
consuming in a production
environment.
This approach is good for
resource-constrained
environments. It is
appropriate for large
organizations only if you are
able to schedule sufficient
downtime, for instance, a
long weekend.
Phased Cutover Low risk with low
development overhead.
Especially conducive to
testing.
May require additional
resources—either more
memory or a second system.
Requires tighter coordination
with application groups and
database owners.
If neither of the other two
approaches seems
appropriate, you can use a
phased cutover.
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